Dare and his team are preparing to land on a planet known as the Green World due to its total coverage in thick jungle. While still on board the ship, a stowaway monkey goes to steal a grenade from Hales, a crew-member. Hales strikes it, an action said to bring bad luck. Dare and his landing party rappel down to the surface, but the trees come alive and attack them.
They use grenades to force the trees back, then Dare and Haley go on the attack, first using bayonets to scale the nearest tree, then swinging on vines to get close to the largest tree which appears to be the leader. They try to use grenades against it but other trees get in the way, sacrificing themselves to protect the leader. Haley swings down to it and detonates his grenade against its base, sacrificing himself for the sake of the team.
- Dan Dare is a veteran space pilot who leads the mission to investigate the lost worlds.
- Bear is an ex-Russian cosmonaut, who was kicked out for his tendency towards extreme violence.
- Hitman is a space explorer who, after an accident in the vacuum of space, now has his gun fused to his hand. He is an expert marksman with it.
- Pilot is an ace pilot recruited by Dare to fly his Space Fortress.
- Haley is one of Dare's crewmen. He attacks a monkey caught stowing away on the ship, incurring the wrath of his crewmates who are convinced it will bring bad luck. Later, on the planet, he sacrifices himself to save them.
Baker, Bronson & O'Neill
- Baker, Bronson & O'Neill are members of Dare's crew. They are all killed by the living trees of Greenworld. First Baker & Bronson vanish, then O'Neill is killed along with another unnamed crew member.
- Haley Junior is a monkey stowing away on the Fortress. When he tries to steal a grenade from Haley, Haley strikes him. The monkey later recovers and is adopted by Bear, who christens him Haley Junior.