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.