The life of an ex-con is never easy, especially when cellmates show up expecting favors. Al Baldwin is a reformed criminal but suddenly has unexpected guests who hide out at his house while plotting their next crime. When that holdup goes bad, the cons hold Al's wife hostage until Dan and the Highway Patrol come to the rescue.
Several criminals conspire to stage highway accidents prompting truck drivers to stop and help victims only to be assaulted and have their cargoes stolen. After discovering the hijackers are being tipped off by the owner of a roadside diner favored by truckers, Chief Mathews creates a ruse to force the crime ring into action with the hopes of capturing them.
Reporter Sam Dalquist has gone missing. Dan has been looking for him because a two bit hood was found dead after getting a traffic citation driving Dalquist's car. The only lead Mathews has is that Dalquist was working on an exposé about a hood named Matlock and that may be where the writer will be found...dead or alive.
Steve Talbot is a jewel thief who likes nice automobiles, and the Highway Patrol knows this. So Talbot flees capture after a job in an old junker. This gets him past the roadblocks but he soon is stranded on the side of the road. He hijacks a newly married couple pulling a trailer and Dan passes the trio through, not wanting harm to come to the civilians. But in passing the blockade, they unknowingly pick up a new rider.
Jerry Watts is the son of a millionaire and he's just been kidnapped and taken to an old shack high in the mountains. After a tip from a game warden brings the Highway Patrol, Jerry tries to escape to the officers, only to fall into a canyon severely injuring himself. The only way out is straight up.