It was the second and final story in the Krynoid audio series, following on from The Root of All Evil. It was not a direct sequel to The Root of All Evil, as, instead of the earlier story's contemporary settings, it introduced the Krynoids into a 12th century setting, pitting them against the Knights Templar.
It was also notable for introducing Saul Jaffe as the human lead, Henri d'Arrée. Although D'Arrée never reappeared, Jaffe would be cast the next year in BBV Productions' own Faction Paradox Protocols series as Sabbath Dei, a major character in the Faction Paradox series and in the BBC Eighth Doctor Adventures.
Medieval legends tell many tales of the Greenwood: magical tales of King Arthur and the Fair Folk; rousing tales of Robin Hood and his Merry Men; and harrowing tales of a monstrous plant demon that could possess men, corrupting their very beings.
When alien pods land in an English forest, will the Krynoids claim another world, or can medieval might and wisdom triumph?
Medicine man Osbert is accompanied by man-at-arms Alfred through the forest as he looks for the herbs he needs to create a cure for the Lady Maud. They bicker, with Osbert unhappy to be saddled with a bodyguard as though he is some defenceless child. However, they soon realise something really is amiss and they are being stalked by a wolf, which surprises both of them, as it is daytime. When the creature shows itself, it is a monstrous hybrid of a wolf and a plant, but no less ferocious than a regular wolf; while Alfred flees, Osbert trips on a root and is left at the mercy of the creature.
Back at the castle, the Earl Godfrey goes to meet a new arrival, wondering if it is Osbert and Alfred returned at last from their expedition into the forest, but it is instead his old friend, the Frenchman D'Arrée. D'Arrée explains that he has come from the hospice because he heard about Lady Maud's illness, and has brought with him Moses of Tyre, a scholar of the Knights Templar. Although he does have the servant-girl Rose escort Moses to his wife's chambers, he is openly suspicious of the newcomer due to him being a Jew, albeit a Christian convert. D'Arrée tries to talk him out of his prejudices. Their conversation is interrupted by the return of a harried Sergeant Alfred, who tells the two noblemen about the mysterious attack and Osbert's disappearance. The Earl orders Alfred to go back into the forest with backup and find Osbert again. D'Arrée joins the expedition.
In the forest, the party of men-at-arms soon come across another plant-monster, similar to the wolf but larger and more humanoid, who soon kills one of the men, Leofric, and wounds another one, Edmund. To the armed men's terror, the creature seems undeterred even after they manage to "wound" it, and they spot Osbert's satchel on its shoulder, revealing that it is Osbert himself, corrupted. D'Arrée orders the other men to fall back, and they make their way back to the castle, empty-handed and chased at a distance by the "forest demon". Moses worriedly explains that he can do nothing for Lady Maud without the herbs to prepare a potion, and decides to ride back to the Temple Hospice to bring back some of the herbs kept in storage there, and also more Knights Templar, armed for battle.
Soon, the "forest demons" attack the village near the castle. Unable to wait for Moses's reinforcement, Alfred's men-at-arms regroup to fight back against the monsters, with D'Arrée mounting his war-horse, Léontif. During the battle, D'Arrée gets a hit on the "Green Man" with his sword after dipping it in holy water at the castle chapel, convincing him and the Earl once and for all that whatever the monster is, it is not a demon. The retreat back into the castle but are soon forced to go back into the fray when Moses of Tyre returns, riding through the village without knowing that the Green Man is there, waiting. Though Moses' horse bolts in fear after throwing him, taking the previous herbs with it, the scholar is able to advise Alfred and the Earl on how to defeat the monster: observing that it is plant-like, he suggests that they should use axes to try and chop it apart, instead of stabbing it with swords and lances.
D'Arrée, Moses and the Earl make their way into the village, trying to recover a supply of axes from one of the houses. They believe themselves to be safe from the Green Man because it is too large to fit through the door, but the creature has also grown strong enough to begin breaking down the wall of the peasant-house to get at them. As they try to flee to the church, the only stone building in the village aside from the Earl's castle, the Green Man startles them by speaking, calling out the Earl by name. D'Arrée goads the entity into explaining its nature, with it explaining that it is a Krynoid, and that "the animal Osbert" no longer exists, having been absorbed into the Krynoid hive mind, although the Green Man still has his memories. The Green Man explains that Osbert tripped on a Krynoid pod in the forest while fleeing from the ex-wolf, as the wolf had done. It further, calmly discusses the Krynoids' plans to take over the entire Earth and absorb all of humanity.
The walls of the hovel finally collapse, but serve as a temporary barricade that buys the humans time to head back towards the castle. On the way, they finally meet up with the Knights Templar summoned by Moses, and give them the axes. The ensuing battle is finally successful, with the Krynoid hacked apart until it is no longer able to move, and Alfred's men-at-arms quickly setting fire to the remains. While the Earl and Alfred go back to the castle with the Knights, D'Arrée and Moses head into the forest to recover their horses, and the herbs for Lady Maud that are still hopefully with D'Arrée's.
In the forest, D'Arrée and Moses discuss the creature, noting to themselves that if Osbert was transformed by finding "a pod" as the Green Man said, there might be others in the forest. As they search, they come across a gruesomely gored wild boar. They realise it was killed by another Krynoid hybrid, the one that grew from the wolf that found another pod. They finally find their horses, but D'Arrée's is attacked by the wolf-Krynoid, now grown to humongous size. D'Arrée starts to tell Moses to hurry back to the castle on his own horse with the herbs, instructing him to advise the Earl to keep the other Knights Templar at the castle, but Moses convince him that it is too late for his war-horse, and to flee with Moses while there's still time.
Fleeing, the two are pursued by the gigantic Krynoid; as they cut through the field and start to catch sight of the village, the sight of the monster causes panic among the villagers, and D'Arrée manages to convince Moses to let him off his horse so that his place can be taken by an innocent woman or child, and so that D'Arrée can help guide the rest of the villagers to safety. As Moses arrives at the castle, Lady Maud's condition is beginning to improve — but the Templars have already left. D'Arrée finally catches up, carrying several children himself, as the castle gets ready for a proper siege. As the full grief of losing his horse hits him, D'Arrée rages and swears vengeance on the Krynoid.
The creature, now almost as tall as the castle walls, starts to throw itself against them like a battering ram — giving Alfred's men the opportunity to use ordinary besiegement tactics, pouring boiling oil onto the creature, which actually does seem to harm it. As it continues to grow despite the wounds, however, D'Arrée suggests using flaming arrows to set the oil on fire and truly kill the beast. However, one of the men-at-arms, Harold, falls off the battlements and is unable to get himself out of the moat as the very weeds start moving under the Krynoid's influence and pull him under, drowning him. However, before long, the siege also lets up as the Krynoid wanders back into the village in search of easier prey, as it is starting to feel "hungry".
The Earl takes the opportunity to go see his wife, who Moses assures him will now be alright in a day or two. As everyone takes the opportunity to eat, Moses and D'Arrée have a conversation about their homes and the politics of Crusades. They decide to go to the battlements to try and get a glimpse of the creature while it's still save, and find that it is returning towards the castle, bigger than before. Moses asks the Earl and D'Arrée why they have not already tried to burn it; they reply that they have, with the oil and arrow, but it did not work. Realising that the Krynoid survived because part of its body was submerged in the waters of the moat, Moses announces that what they need is a substance that will burn even underwater. He claims to be able to make such a material: Greek fire.
However, as the Krynoid attacks the castle with renewed vigour, Moses comes back from the castle's storerooms to announce that they are missing a key ingredient of the incendiary mixture, sulphur. D'Arrée volunteers to ride back to the Knights' hospice to get some, borrowing one of the Earl's horses. They manage to burn away the anumated weeds in the way of the drawbridge while the monster is probing a different area of the walls, but while D'Arrée rides out, the Earl ends up on the outside as well when the drawbridge has to be raised again in a hurry to stop the Krynoid getting in. Shouting at Alfred that he's in charge of the castle until D'Arrée and he return, the Earl has no choice but to come along. Their ride is a perilous one, as the road to the hospice runs close to the forest, whose trees have also been animated by the Krynoid's influence.
Back at the castle, Alfred and Moses observe the Krynoid battering against the wall in a curious pattern, hitting with two tendrils in quick succession over and over, but never both at once. Just as Moses remembers what the sound reminds him of — soldiers marching over a bridge — a crack finally appears in the walls. Moses finally realises that the Krynoid is not just trying to create a breach through the wall, but collapse it entirely. When the Earl and D'Arrée return with the sulphur, he prepares the Greek fire successfully — but all seems lost when the wall finally collapses and the Krynoid begins to enter the inner courtyard. Moses, however, had Alfred and his men transport the catapult onto the other battlement, facing inwards, since he had predicted that the main wall wouldn't withstand much longer.
The Greek fire is successfully hurled at the Krynoid, which is then fired at with more flaming arrows. To the surprise of all involved, it not only burns, but explodes. Moses is left speculating that the specific mix is created is a new substance, even more potent than Greek fire, muttering that it may be his somewhat unorthodox addition of charcoal to the recipe which made the difference. Marveling at the military possibilities of Moses's invention, the Earl resolves to tell King Richard about it. When Rose brings word that Maud is wholly awake now, however, the Earl goes to her, but seems to dread the prospect. He explains to an amused D'Arrée that, victory or not, he is afraid of having to explain to his wife how the castle got into such a dreadful mess.
- Earl Godfrey - Arthur Bostrom
- Henri d'Arrée - Saul Jaffe
- Moses of Tyre - Keith Drinkel
- Osbert/The Green Man - Nigel Fairs
- Sergeant Alfred - Michael Chance
- When first coming to face with the wolf-Krynoid, Alfred states that it might be a demon. He also likens to the beast to tales he has heard about "the hounds of Hell".
- D'Arrée has a beard.
- Osbert is Earl Godfrey's herbalist.
- The Knights Templar are also known as the "Knights of the Temple of Solomon". The emblem of their order depicts two men on a single horse.
- Henri d'Arrée calls his sword Durendal, after another sword "of old".
- Moses of Tyre's wife was killed during the Crusades, and, as he euphemistically tells the Earl, "not by the Saracens".
- D'Arrée does not believe in ghosts.
- Moses believes that "the Lord keeps some secrets from [humanity], and for good reason".
- Moses and D'Arrée wonder if the boar they find was killed by a bear.
- D'Arrée describes himself as a Breton.
- Tyre is located on the Mediterranean shore.
- Earth is attacked by Krynoids, who display the ability to grow to gigantic sizes. (TV: The Seeds of Doom, AUDIO: The Root of All Evil)