Young Greek fisherman Nick Evangelides unwisely agrees to sponsor 'Doc' Roberts and 'Girlie' Piper's scheme to bring Greek girl Lina Zangalis to Australia for prostitution purposes. Lina is under the impression that she was brought to Australia to marry Nick, and when 'Doc' Roberts is later murdered, Nick becomes the prime suspect.
Two youths, thinking a fruiterer keeps a lot of cash at home, break in while he is at work. His wife is tied up and gagged while they ransack the house. Finding nothing, they decide to question her again, but when her gag is removed she screams for help. The youths panic, and in their attempt to silence her they bash her to death. They flee empty handed just as the fruiterer, Sergio Conte, returns. He recognises one of them as a customer at his shop, and he swears to avenge her death and sets out to catch the Killers before the police. This leads to a race between detectives and Sergio to find the killers, and results in a dramatic chase through an underground tunnel system.
Art student Martin Cooke becomes involved in murder when prison warden Tom Richards is shot and wounded, and his wife and small son are shot dead as they relax in the Botanic Gardens. An artist's sketch book found near the bodies is the only clue and leads Homicide detectives on a search through art schools.
Aboriginal boxer 'Flash' Johnny Miles, training for a championship fight, becomes jealous of his sparring partner's friendship with his wife. In the ring Johnny hits him so hard that he appears to have died as a result. Sen. Det. Patterson is planted undercover as the new sparring partner, and police uncover a plan to 'throw' the fight.
The discovery of a skeleton in the wall of an old home that is being demolished opens up many memories for Inspector Fox when he realizes the home belonged to Karen Richter, the girl he loved in his youth. The other Homicide detectives become concerned when Fox seems hesitant and apparently unwilling to investigate the case.
Model Karen Healey becomes involved in an attempt to murder ruthless businessman Robert Morton. Morton made his fortune by crooked business deals and swindles. He realizes his life is in danger when he finds a doll in his apartment wearing clothes identical to his own with a noose around its neck. Later, Morton's car is blown up, killing his bodyguard.
Patterson solves a ten year old case and Supt. Tilley awards him a commendation. Eddie Patterson, Jim's twin brother visiting from Sydney, is somewhat crazy and nearly always drunk, and is seen by Supt. Tilley at a lively evening at a club. When Tilley meets Patterson, he mistakes Jim for Eddie, and is aghast at his behaviour. Further reports reach Homicide about Eddie, and they become concerned about Jim's 'split personality'.
A young Italian girl, Maria Bompani, is in love with a young playboy. She asks a priest about atonement - if she kills her boyfriend and then herself, is her sin paid for? Before Father Gilbert can answer her, she flees from the church. A silver locket which she dropped is the only clue to her identity.