Jim's shackled to his ex-parole officer Marcus Aurelius (Louis Gossett Jr.), now a PI himself, when a no-holds barred competition for a new NBA franchise ensnares both sleazes. Jim can't figure which jock-sucker, the motor mouth Marc works for, but whoever it is, they keep bringing Jim the pain and costing him way-too-many non-reimbursed expenses. As a PO, slick Marc tried to send Jim back up the river; as a PI, he runs Jim dizzy dodging bullets.
Hoods snatch a stockbroker, and his sister hires Rockford for $23.64, because Jim's in the yellow pages and her big brother instructed her not to dial the cops. Jim's protective of the naive 25 year old bookkeeper, despite the tiny fee, because he fears her brother is dead, and she can't accept that her only relative, who's always taken care of her, may be mixed up in a securities scam.
A farming hub has more business than it can handle, including giving Rockford the business. The PI's car breaks down near the boomtown, after a source Rockford contacts in a divorce case steers Rockford there. While his car is being worked on, Rockford is quickly entangled between an underage motel worker and her jealous cop boyfriend, and in a double-cross over a narcotics deal. Is it just another tricky day for unlucky Jim, or is bucolic New Pastoria a sunny sin city ?
The Rockfords work with Sgt. Becker to solve Rocky's friend's murder. When 6 tractor trailers from the same depot are hijacked by a gang, there must be a connection with the killing, but who desperately needs tons of ladies' underwear, grapefruit and dynamite ? The proud Rocky resents Jim taking care of him, making the slew of hit-men even harder to combat for Dennis and a very confused LAPD.
Rocky is targeted for death after seeing a meeting between a truck dispatcher and a crooked executive. Jim wants desperately to protect his father but discovers he hasn't been keeping up with Rocky enough to even find him on a typical day. The dispatcher was giving the supposedly-retired Rocky work as a trucker, so when Jim discovers the dispatcher dead in a crate bound for Malaysia, the police figure the elusive Rocky knows why.
Dennis pleads with Jim to untangle him from a timeshare con, without Dennis' boss, Jim's nemesis Lt. Diehl, finding out he's a victim too. Rockford's a lot more interested when a friend of Dennis' who's also an unhappy vacation homeowner, proves very helpful, and happens to be a gorgeous single blonde. Jim recruits his father and Angel to out-scam the scammers.