Cardiff Docks. A cargo ship docks and Bronik is paid off and cheerfully debarks. He makes his way to his old apartment, expecting to find his girlfriend, Anya. Stashing his belongings in the hall cupboard, he enters, but finds another girl, Christine, now living there. After an emotional exchange with Christine and the landlord, Doctor Das, he gets Anya's new address, after paying off her debts to Dr. Das.
Bronik finds Anya at her new apartment and argues with her in Polish. Realising she has another man, he pulls a gun and shoots her. He hides the gun behind the gas meter in the stairway outside.
A young child, Gillie, witnesses the killing through the letterbox. She takes the gun, but Bronik sees her, although he can do nothing as other people are around. Barclay, Anya's other man, arrives. As Barclay enters the apartment, Bronik makes his escape. The neighbours ignore the shots, assuming they are Gillie's toy caps.
A neighbour, Mrs Parry, discovers the body. The police arrive, and Superintendent Graham questions Gillie and her aunt, Mrs Phillips, who is hostile. Gillie gives a false description of Bronik. The police allow Gillie to leave to sing at a local wedding. Bronik tracks her down at the church. After the wedding service, he chases her and wrestles the gun from her. Afterwards he strikes up a friendship with her, promising to take her to sea if she helps him escape.
Gillie has swapped the single remaining bullet from the gun with her friend Dai Parry. Dai's mother finds it and calls the police, who establish that it came from Gillie. Bronik and Gillie leave that night; Bronik visits a pub to find a list of ships leaving shortly. He hears a radio announcement of Gillie's disappearance. Avoiding patrolling police, Gillie leads Bronik to a ruined cottage in the country.
The police interview Barclay about his affair with Anya. Although Barclay - a married, well-known local radio sports presenter - discovered Anya's body first, he didn't report it for fear of damaging his career. It emerges that he had left his own gun at the scene.
Next morning, Bronik wakes Gillie and tells her he must leave without her. After he leaves, Gillie is caught when a tourist coach party recognises her from a newspaper picture.
Superintendent Graham interviews Gillie, who accuses Barclay, picking him out at an identity parade; however she makes a mistake, claiming that Anya and Barclay were both arguing in Polish. Christine has brought in Bronik's belongings, and the police have found a photograph of Bronik with Anya, but haven't identified him.
Bronik returns to Christine's apartment to retrieve his belongings. He is devastated, believing Christine has handed in his passport and papers. But when Christine gives them to him; he thanks her profusely and leaves. The police discover Bronik's identity from Dr. Das's records.
Bronik bribes a shipping clerk and Caracas, First Officer of the Poloma, a ship leaving on the afternoon tide, to include him on the crew list. He boards the ship, which is soon towed out to open water. Under international maritime law, once he is 3 miles offshore the police cannot touch him. But the police are already on his tail.
With Gillie in tow, the police arrive at the dock to see the Poloma offshore. They radio ahead to have the Barry pilot waiting for them, then race along the coast road to Barry, where the Poloma will pass closer to land. They pick up the pilot and head out to board the Poloma, where they confront Bronik.
The Captain and First Officer are hostile; the First Officer determines that they have crossed the 3 mile limit and are therefore not subject to British law. Superintendent Graham requests a radio fix from Cardiff, but this confirms the Poloma's position.
Gillie wants to stay with Bronik, but every minute she stays on board reduces his chances of escape. Gillie runs and hides on the ship, but falls overboard. Bronik hesitates, then dives in to save her, knowing he will lose the protection of the Poloma. Bronik and Gillie are picked up by the police. Superintendent Graham commends Bronik for his bravery.
