Joe Yateley, known as Tom, arrives at Hawlett's, a ballast transport company, looking for driving work. The terms are tough - the emphasis is on speed, whatever the weather, with the drivers responsible for their own vehicles, and any speeding fines. The manager, Cartley, sends Tom on a hair-raising test run. Despite two near accidents, he passes.

Tom takes a room at Ma West's with most of the other drivers. He meets Gino, who has been using Tom's room as a place to pray. Gino talks about the job, and about Lucy, Cartley's secretary and Gino's girl. At the café, Tom meets the other drivers, and Tom has a run in with the aggressive Red, the dominant member - and fastest driver - of the team.

In his number 13 truck, Tom competes with Red, in truck number 1, and the others for the trophy for most runs of the day - a gold cigarette case. Red drives recklessly and uses intimidation to win. Tom discovers Red's secret: he takes a shortcut through a quarry.

At the café, Gino warns Tom that the shortcut is dangerous. Outside, Tom meets Lucy, who flirts with him. Gino arrives and, unsuspecting, invites Tom to join him and Lucy at the cinema. Tom declines and tells Gino he intends to win the trophy; Gino tries to dissuade him, but reluctantly agrees to help.

Next day, Gino blocks Red's truck to give Tom a head start. Red gets his own back by driving Gino off the road. In the café that evening, Red warns Tom that he is not only the pacesetter, but the road foreman: he can make things difficult if Tom gets out of line.

The drivers attend a local dance. In the absence of Gino, Lucy flirts furiously with Tom. A local man objects to one of the drivers dancing with his girl, and the evening degenerates into a fight. Tom leaves; Red and the others call him 'yellow' and vow to get him.

That weekend, Tom visits his mother and brother Jimmy at their tobaccanist's shop. Jimmy is pleased to see him, but when his mother returns she is hostile. Jimmy is crippled after an accident, for which Tom served a year in prison. Jimmy doesn't hold Tom responsible, but his mother is unforgiving. Tom leaves, dejected.

The next week, Tom finds the other drivers ganging up against him, urged on by Red. Frustrated, Tom tries the quarry route, and equals Red's total. That evening, Gino offers to swap his truck plate number, 3, for Tom's number 13, so the others will think he is Tom, and Tom will get a clear road to beat Red.

Tom finds his pay short and he and Red get into a fight, which Tom wins. Inspecting his truck, Tom finds evidence of tampering, but is distracted by Lucy, who has come to tell him she has left Gino. Tom is angry at first, but soon they kiss. Later, Gino sees Tom getting out of Lucy's car.

Next day, Tom buys a one-way train ticket for London, but Lucy finds him at the station: Gino has been hurt. At the hospital, Lucy tells Tom that Red and Cartley are running a scam, hiring fewer drivers than the head office pays for, and sharing the rest of the money. Gino is dying, but manages to tell Tom that he switched the numbers as he said; Tom realises he was the intended victim.

Tom heads for the yard, where he threatens to expose the scam unless Cartley pays the drivers the money they deserve. Cartley tries to bribe him, but Tom rejects him, taking Red's truck. Red follows with Cartley in number 3. Lucy gives chase in her jeep.

On the quarry road, Red tries to run Tom off the road, leaving him perched precariously on the edge. Red tries to go back, but he can't brake: he realises he has Tom's truck, with tampered brakes; he and Cartley career over the edge. Tom escapes his truck just before it slips over. As he watches it fall, Lucy runs to him.