As a detective working for an elite undercover squad, Dan "Spider" Shepherd has lied, cheated and conned in order to bring Britain's most wanted criminals to justice. When a powerful drugs baron starts to kill off witnesses to his crimes, Shepherd is given his most dangerous assignment yet. He has to go undercover in a top security prison - a world where one wrong move will mean certain death. Corrupt prison officers, lifers with nothing to lose, and hard men with something to prove are all gunning for Shepherd. The only way to survive is to play his role to perfection, twenty-four-seven, among criminals for whom violence is a way of life. As he gambles everything to move in on his quarry, he soon realises that the man he is set to trap is even more dangerous than the police anticipated. And that he is capable of striking outside the prison walls and hitting Shepherd where it hurts most.