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.

Playing his role to perfection, Shepherd gambles everything to move in on his quarry - only to realise that the man he is set to trap is even more dangerous than the police anticipated.