After a bungled raid which kills an innocent man young DS Steve Arnott faces disgrace. However he is transferred to the anti-corruption squad, whose head, superintendent Ted Hastings, gives him a "very special case" to investigate - DCI Tony Gates, recently awarded a medal for heroic conduct but with a suspiciously high arrest rate. Hastings tries to get Gates on minor bribery charges, in vain, and is unaware that the married Gates has covered up a fatal hit-and-run by his lover, businesswoman Jackie Laverty. Meanwhile DC Kate Fleming joins Gates's team and tells Steve she is investigating him from the inside following the deaths of two drug dealers.

Gates, knocked unconscious by the attackers, tampers with evidence, hiding a whiskey glass before police arrive to find Jackie has vanished. He claims he has just got there himself. Hastings and Arnott quiz him on his relationship with Jackie and he admits she was an old flame but denies knowledge of her money laundering. Arnott goes over the top in confronting him with evidence to suggest he was at Jackie's house when she was killed but makes himself look desperate. Gates is taken off the case and later, whilst investigating Wes's murder, is grabbed by masked men and an evil child who threaten to frame him for Jackie's murder unless he takes over her money laundering racket.