Snatched from his bed in the middle of the night, Ollie Turner is thrust into a world of danger and excitement.
Below the streets of London he discovers a secret city: a network of tunnels that lead him to the Haven, a sanctuary for kids run by kids, and the headquarters of an organisation that fights for justice everywhere.
Soon Ollie is caught up in the Haven's battle: a quest to stop 'Mad Maddy' Sikes from destroying the city. But time is running out for Ollie and his new friends. Will they manage to stop Sikes before it is too late? And who is the traitor in their midst?