In the summer of 1295, a Welsh quarryman, Brac, discovers what looks seems to be a valuable stone in the quarry at Rhuddlan. Looking to deny the local English lords such riches, he encounters and offers the stone to two travellers in a tavern. Brac takes the travellers, representatives of the Knights Templar and who are searching for such an object, to the quarry in the dark of night to remove it. Retrieving the stone, the group has to flee as the alarm is raised by the English garrison. One of the Templars, Eleanor de Molay (also known as El), distracts the chasing English whilst Brac and the other Templar, Sir Henry, flee into the night. Eleanor is taken to Rhuddlan castle and shown before Lord Reginald de Grey, who knowing her to be the niece of the Templar Grand Master Jacques de Molay, sends her on her way to Chester for trial. The caravan transporting El is attacked by Welsh brigands en route to Chester. In the fighting, El escapes and flees south on a horse. Close to exhaustion, El arrives at a Welsh village called Llaneurgain, where she is given rest. English soldiers arrive in pursuit of her, causing trouble with locals. A fight breaks out, for which El feels responsible, that is brutally finished by two crimson-cloaked riders belonging to the Dragons outlaw group. Knowing her identity, they warn El to leave quickly.
Sneaking the stone into the city of Chester, Henry and Brac find Prior Simon at a tavern, who reluctantly offers them refuge at Chester Abbey. At the abbey, Simon and Abbot Thomas Birchills investigate the stone with Henry and Brac, accidentally discovering that it reacts to flame and, in a burst of blue effervescence, causes objects around it to vanish. Having discovered the stone’s whereabouts, Reginald arrives with a knight, Sir Edward de Beauchamp, and armed men at the abbey in search of the fugitives. Henry and Brac have fled, but Abbot Thomas insists on demonstrating the strange features of the stone. The gathered crowd, including Mother Alice de Pierrepont and Sister Agnes of the Chester Priory, are shocked by the demonstration. Reginald vows to take the stone to London and write to every lord in the kingdom about its powers.
Henry and Brac are on the road to the London Temple. Chased down by two crimson-cloaked riders, Henry confronts them, knowing them to be Dragons. The Dragons know who he and Brac are as well, and quickly a confrontation becomes violent. Brac decides to go with his fellow Welsh, leaving Henry to travel back to London alone.
Comte Mathieu de la Marche, spymaster to King Philippe le Bel of France, separately meets with Le Gris and Comte Jean Lemaître de Chartres to discuss the deteriorating fiscal situation in the kingdom, as he awaits news of the French campaign against the English armies in Aquitaine. He discovers the Templar Knights plan to call in all their loans to the French king, which would leave the crown broke. News of the French victory in Aquitaine arrives.
Later, a general council is held at the Louvre, with many in attendance. Robert de Bourgogne addresses the attendees, detailing the French victory. Guillaume de Troyes speaks on the Flemish and Aragonese, encouraging Philippe to invade Flanders, allies of the English, to press home their advantage and cut off the English from the lucrative wool and cloth trade centred in Flanders. Philippe declares there will be no more fighting, on the advice of his confessor, the Archbishop of Sens. Mathieu suspects deceit but holds his tongue until meeting privately with the King after the council. Philippe demands that King Edward of England pay him homage in person and renounce his title of Duke of Aquitaine. Privately, Philippe admits to deceit and instructs Mathieu to stir up trouble in Flanders and Calais, the latter of which nominally a French possession but with a powerful merchant class. Philippe reveals ambition to conquer and reunite England with France under the Capétien dynasty. He also instructs Mathieu to delay the Temple’s collection of their loans.
Mathieu speaks to the Master of the Paris Temple, Matthew Norris, requesting the Temple extend their loans. Norris refuses, and criticises the King’s opposition to paying tithes to the Church. Returning to his house, Mathieu goes to see his wife, Jaqueline de la Marche, who he loves dearly but she does not reciprocate the feeling. Mathieu reveals he is leaving for Flanders, but Jaqueline declines to go with him. She mentions correspondence with their son, Luc, who is at the family home in Guéret. Mathieu is called to a upper council meeting with King Philippe, Queen Jeanne de Navarre, Lemaître, Raoul de Clermont, Robert de Bourgogne and Charles de Valois. Like Mathieu, Jeanne and Robert have considerable influence on the King, who is becoming more aggressive. The council discuss financial and military matters. Jeanne suggests that Philippe conquer the wealthy county of Flanders to bring income to the crown, taking men away before they are needed for the harvest. In an attempt to derail the invasion, Mathieu suggests taxing the Church as a means of income, but Philippe decides to go with both. Leaving the meeting, Mathieu reads again a message from a source in England, revealing that King Edward now has a powerful relic.
Brac and the two Dragons are riding west. Brac has growing regret over the choices he has made since discovering the stone. He attempts to flee but is caught by the Dragons, who explain that the stone is a gift of God, and Brac is the Black Knight of old legend, divinely ordained to take this role. Encouraging the doubtful Brac, the Dragons tell him he has a duty to all Welsh to help remove the English invaders.
Adelaide, gaolkeeper at Clun Castle, is torturing a captured Welshman for information - Madog ap Llywelyn, the last Prince of Wales. Adelaide reveals the loss of her daughter to Dragons, fuelling her anger at the prisoner, who denies being one of them. Removing parts of his hand, Adelaide extracts information that the Dragons are concentrating at Dolwyddelan in North Wales. Adelaide informs the castle sergeant, Everard. He in turn tells her she will be joining Humphrey de Bohun’s army that has set out to crush the Dragons, because of her insight into the Dragons through torturing many of their number.
El is psychologically traumatised by her experiences and resulting sense of guilt. She returns to the Round Church (the Templar headquarters in England), surprising Henry, and the pair share an emotional reunion. Guy de Foresta, Templar Master in England, joins and discusses the importance of the stone. He reveals that another relic was previously found, and
After her traumatic experiences in and on the way back from north Wales, Guy forbids El from attending the demonstration for her own protection. The Temple Master strikes a deal with Abbot Geoffrey for Sir Henry to attend the stone, now popularly known as the Godstone, undercover amongst the Crutched Friars, the Order chosen to accompany the stone to the demonstration at the Tower Liberties. This is so that he might later gain access to the Tower with the stone as part of a plan to steal it for the Temple. Huge crowds fill the streets around the Liberties, a field stretching up the hill from the Tower of London. Walking in procession with the Crutched Friars, Sir Henry sees many people crushed as the crowd surges for a glimpse of the stone.
The gathered nobles and churchmen are in attendance at the top of the hill, with principle guests at the stone itself. These include Antony Bek, John le Romeyne, Robert Winchelsey (an enemy of the King), the papal legate Bartolomeo Fiadóni, and Lord Reginald de Grey. King Edward arrives with his guard from the Tower, at which point Sir Henry notices two of the other Crutched Brothers are secretly dropping oil from beneath their clothing. Realising the danger that fire poses around Godstone, Sir Henry speaks out and warns everyone to flee, only to be arrested along with the guilty monks. The Godstone is carried back towards the Tower and the King flees.
In the crowded streets, El has disregarded Guy’s command and left the Round Church with the stable lad Maxwell. She sits on his shoulders so as to gain a better view of any suspicious activity, fearing the demonstration a ripe target for their enemies to attack. She also spots a number of houses with gaping holes in the roof, presumably from people trying to gain a better vantage point. In the crowd, a nun, Sister Diane, finds her and reveals she has been sent by Abbot Geoffrey of the Crutched Friars. She warns of an infiltration of the order and some possible dangers about the demonstration. At this moment in the field, flaming missiles fly in from the city, over the houses bordering the field. They land and ignite the oil dropped, sending flames roaring across the field in all directions, suggesting the area to have been thoroughly soaked. Many spectators die in the flames and in the resulting panicked crush as hundreds seek to flee the fire.
In the city, El and Maxwell reach one of the previously-noted houses with a hole in the roof. A man emerges from the stampeding crowd and tries to attack El in an apparently targeted attack, but she manages to slay him first. Horrified with her actions, she sends Maxwell back to the Round Church and climbs up the house to see the cause of these missiles. El finds two men packing up powders and equipment, before one kills the other. El jumps in to fight the remaining man, but he escapes downstairs. She gives chase only to find the King’s guards waiting for her at the entrance to the house.
In the chaos, Henry evades the guards who have apprehended him, and he helps people struggling to escape the flames. As ever more flaming missiles crash into the fire, Reginald runs to the Tower’s gatehouses to ensure the King makes it to safety through the panicking crowds, and to ensure the stone has reached safety within fortress’ walls. To his alarm, smoke begins to rise from the middle gatehouse. Having arranged the safe escape of the crowds around the Tower, he enters the outer gatehouse just as a blinding blue flash precedes a terrific detonation that reduces the middle gatehouse to nothing. Amidst the devastation, Reginald and his men fight through to the scene of the detonation, and to their relief find the King has made it safely to the inner gatehouse.
King Edward, Reginald, Sir Ralph Sandwich, Sir Walter de Beauchamp, John de Warenne and John Droxford gather in the White Tower of the fortress. The Dragons are assumed to be responsible. They ponder how to respond, discussing the roles of Sir Henry, Eleanor de Molay, and Guy de Foresta in the current predicament. They also reflect on news from the continent, where the French king’s conquest brings him closer to the coast and a possible invasion of England. Surrey says that he will take ships to France to disrupt their fleet.
Reginald and Surrey visit the site of the middle gatehouse and the efforts to search for the Godstone amongst the rubble. Reginald realises that the detonation has caused the bodies and rubble to disappear, and to their horror a body is discovered cleaved in half, with the other half missing.
Hereford leads his army, including Adelaide, into the Welsh hills. A scout brings back a Dragon rider, Gwenhwyfar, who is their leader. Hereford goes to talk with her. After tense discussions and the sudden appearance of the Welsh forces, he announces to surprised onlookers that the two sides are to be allies, having already planned such a move. Gwenhwyfar brings her infant with her as a sign of trust and good intentions. This riles Adelaide, who lost her own child in an attack by the Dragons. Adelaide physically attacks Gwenhwyfar but is quickly restrained and no harm is dealt to the alliance, nor do the Welsh attack the English in response.
Hereford’s army stops at a bluff above the village of Dolwyddelan. Hereford delivers an oration to his men, rallying them to the true purpose for their march – rebellion against the King and the Norman lords, to be achieved by siding with the Dragons. Hereford tells them he seeks to unite the island of Britain under the command of the reborn Arthur, whose arrival has been announced with the stone’s discovery. The common soldiers rise to the speech, heartened by the earl’s rhetoric. The soldiers with Adelaide are convinced, telling her they would follow wherever Hereford leads.
Gwenhwyfar meets with Hereford. The earl questions where her promised king is, and how legitimate he actually is. Gwenhwyfar snaps back, stating that the Dragons have their entire existence at risk for this rebellion. There will always be an England but might not be a Wales. She leaves, and Adelaide goes to Hereford, and he explains that they will retrieve the Godstone and fulfil the prophesied return of Arthur. Hereford wrote to nobles across the country, inviting them to join his rebellion. Hereford also tells Adelaide that he needs her because she knows the Dragons better than he does.
King Philippe has gone back on his word and invaded Flanders, striking at Ghent, one of the wealthiest cities in Europe. The Flemish army, led by Guy Dampierre, lines up in the field aiming to take advantage of terrible conditions and bring down the famed French heavy cavalry. Observing the first charge descend into ruinous slaughter, Mathieu de la Marche and the French reserves ride into battle in a desperate attempt to turn the tide. Mathieu is dehorsed and suffers grave injuries, losing consciousness.
Mathieu awakens, grievously injured from battle, unsure as to where he is. A French voice welcomes him, belonging to his scribe, Pascal Sagittaire, and the comte realises he is in a French hospital and they have won the battle. King Philippe enters and praises Mathieu for his valour in battle, and also to relay the death of Duke Robert de Bourgogne. Following Robert’s death, Philippe appoints Mathieu his Grand Chamberman. Peter von Aspelt, ambassador to the Holy Roman Emperor Adolphus, arrives at the camp. Mathieu interrogates the ambassador as to the Empire’s intentions, especially given the English and Flemish had paid the Empire for support against France that never came. Mathieu and Peter cross swords on other issues, including how to restore the collapsed Flemish wool and cloth trade. Mathieu receives a message from the abbey at Saint-Germain-des-Prés, where his son has been sending letters to his wife.
As winter draws, two Templars, Richard of Kent and Haraldur, arrive at a freezing, snow- and windswept island, each bringing a ship from London. They visit a local house, belonging to Thorfridr (also known as Tova), a Templar who has lived on the island for ten years. Surprised to find her with an infant child, they each deliver a letter to her and then take their leave. The letters are the same, both requesting she bring back something referred to as ‘the wheel’. Overcome with emotion at the request, Tova resolves to immediately set sail. Upsetting the Templars and her friends in the village, including Hulda and the ancient priest, Tova demands that the ships be readied. She goes to the vault in which the wheel is held, only to find it empty.