Plot

Harry Crumb is a bumbling and inept private investigator who is hired to solve the kidnapping of a young heiress which he's not expected to solve because his employer is the mastermind behind the kidnapping.

Harry is the latest generation of the Crumbs, famous and extremely talented detectives. Unfortunately, talent seems to have skipped a generation and Harry is reduced to "gumshoe" work at a remote branch of the Crumb Detective Agency. Back at headquarters, Crumb executive Elliot Draison hatches an evil plan which requires the inclusion of an incompetent detective. With Harry Crumb on the case, Draison thinks everything will run fine for him. Despite his best efforts, Crumb actually makes some headway in the case.—Murray Chapman <muzzle@cs.uq.oz.au>

Over the opening credits, a young woman named Jennifer Downing (Renee Coleman) is kidnapped by an unseen person while taking a mud bath at a spa.

The next day, at Crumb and Crumb Investigations in downtown Los Angeles, Jennifer's father, P.J. Downing (Barry Corbin), a wealthy shipping owner and his trophy wife, Helen (Annie Potts), meet with Eliot Draisen (Jeffery Jones), the president of the detective agency. P.J. wants to hire Eliot Draisen himself to investigate Jennifer's kidnapping, but Eliot claims he has no one available to take the Downing case. Upon P.J.'s insistence, Eliot decides to assign Harry Crumb (John Candy), the grandson of the firm's two founders.

That evening in Tulsa, Oklahoma, Harry, disguised as an elderly window washer (with black-face makeup, a fake bush mustache, fake eyebrows and a gray 'fright wig' resembling the hairstyle of boxing promoter Don King), is ten stories up, alongside a seedy high-rise hotel and photographing a couple having an affair. When the couple move into another room, Harry rocks the suspended platform like a pendulum. He falls off the platform, grabs a rope and swings through an apartment window, landing in an easy chair.

The next morning, Harry shows the photographs to his wealthy client, Mrs. MacIntyre (Michelle Goodear), only to discover he followed her by mistake. He gets called to come to the head office and takes a bus to Los Angeles, California. Upon meeting Eliot Draisen, Harry recites the Jennifer Downing case from memory. When he asks why there was no reference to the stolen jewels, Eliot informs him it is a kidnapping case. Harry leaves and Eliot telephones Dwayne (Doug Steckler), the animal trainer who is keeping Jennifer Downing in a cage, to tell him Harry is a bigger idiot than he had hoped for.

At the Downing mansion, Harry gets his crotch soaked while standing over a sprinkler before meeting Nikki Downing (Shawnee Smith), Jennifer's younger teenage sister and Helen Downing, Jennifer's stepmother. Harry then meets P.J. in his study, who is assembling fishing lures. Harry shows off more of his bad-luck clumsiness when he puts his hand in an aquarium and a dog fish latches on to it. As P.J. tells him Jennifer is his favorite daughter, Harry leans on the desk and impales his hands on several of P.J.'s fishing lures. Harry looks out a window to see Helen flirting with her tennis coach, Vince Barnes (Tim Thomerson). As Harry throws darts at a nearby dartboard, his final bull's eye dart hits a little too hard, upon which the dart board falls off the wall and crashes on top of one of P.J.'s mini ship models.

Harry, disguised as DeRoach, a bearded Hungarian hair stylist wearing blue leather with a shaved head, goes to the spa to interview the woman who gave Jennifer the mud bath that ended in her kidnapping. While re-enacting the crime, Harry leans over a mud-encrusted woman and his fake chest hair falls into her crotch. Slamming his fake hair back on his face as a beard, Harry learns from the attendant that Helen insisted Jennifer take her spa appointment on the day she was kidnapped.

That night, P.J. receives a ransom note requesting $10 million. As he and Harry confer, Detective Casey (Valri Bromfield), a hard-boiled LAPD female police detective, arrives to take control of the case, stating her belief that all private investigators are incompetent slime. Meanwhile, Eliot meets Helen in the horse stables to inform her of the ransom note before pouncing on her. She fights off his romantic advances, telling him he is not rich enough to sleep with her. After dinner, Harry befriends Nikki, who tells him Helen is a money-grubbing nymphomaniac. Harry voices his suspicions that Helen is the kidnapper and makes Nikki his assistant.

The next day, Harry and Nikki use cardboard periscopes to spy on Helen and Vince Barnes as they soak in a hot tub at the marina. Harry is too far away to hear Helen complain that it took her two years for P.J. to put her in his will and now the kidnapper is going to get P.J.'s fortune. Vince suggests they kill P.J. before he pays the ransom. Harry slips off the roof that he and Nikki are on and lands atop an overhead ceiling fan at a local restaurant, where a young boy pulls the lever and makes the fan go faster and faster.

That night, Vince and Helen "fix" the brakes on P.J.'s car.

The next day, Harry bursts into Eliot's office, declaring that Helen is the kidnapper and having an affair with Vince. Eliot is clearly distraught over the news, for he had decided to continue trying to win over Helen's affections.

Later, Vince and Helen leave the mansion after seeing P.J. getting his car. However, Harry and Nikki ask to borrow the car. As Harry tails Helen and Vince, he confides to Nikki that he feels that he is living in his father's and grandfather's shadows and Nikki admits she feels jealous of her sister and always feels she is living in her shadow, as well. Harry believes Jennifer should feel jealous of Nikki. As they go down a hill, the brakes give out. Harry steers between oncoming traffic until he rear-ends Vince's car and locks bumpers. Vince speeds up, dragging Harry with him until they hit a bump, sending Harry's car into a small orange tree.

After P.J.'s mechanic confirms the brakes were tampered with, Harry rightfully assumes that Helen and Vince were responsible, but he continues to mistakenly think that he was the intended victim, not P.J. Afterwords, Nikki tells her father she is helping Harry with his case. P. J. instructs her not to bother the detective, but Harry insists Nikki has been a great help.

Later, Harry disguises himself as an Indian air-conditioner repairman (complete with a turban and brown-colored face paint) and smuggles Nikki into Vince's apartment building in a large toolbox. Harry climbs into an air vent while Nikki directs him, using a short-wave radio. He hears Vince and Helen talking but is unable to see them through the vent. Meanwhile, Eliot Draisen telephones from a booth outside the apartment building and tells Vince that he is late for a tennis lesson at the country club. When Vince leaves, Eliot enters the apartment and blackmails Helen for sex. While Helen goes to the bathroom to freshen up, Eliot turns on the TV set and watches an old film-noir movie in which the two characters discuss killing the woman's husband and absconding to Buenos Aires, Argentina. Eliot voices his approval and decides to follow their example, once he receives the ransom money. Harry, thinking it is Vince talking, works a camera through the vent to take photographs. During the lovemaking, Helen complains the room is too hot, so Eliot turns on the air conditioning, causing Harry to be blown into the apartment manager's (Joe Flaherty) office, knocking the manager unconscious.

That night, Eliot delivers another ransom note to the Downing mansion, stating the money must be paid by Friday, but Helen gets it first and alters it to read payment is due Monday (to give her and Vince more time to kill P.J.). The next day, Harry gives Eliot the photographs, claiming they show Vince and Helen engaging in sex. Eliot looks at them and is stunned to see himself coupling with Helen, but is amused and relieved that Harry seems ignorant. Harry admits he did not take time to look at the photos and brags that he has so unnerved the kidnappers that they have changed their plans and shows Eliot the altered ransom note. Harry then causes another accident when he gets on a stationary exercise bicycle and inadvertently releases the brake, which cases the bicycle to crash into Eliot's dinosaur egg display shelf.

At the mansion, P.J. receives a phone call from Jennifer while Harry, Eliot and Detective Casey listen in. Jennifer pleads that she will be killed if the drop is not made at noon today. Jennifer instructs that the ransom money be dropped off at a phone booth at the Hollywood Park horse racetrack. Casey suggests they bug the ransom money suitcase. Harry agrees to drop off the briefcase containing the ransom as long as police stay out of his way. As instructed, Harry goes to the racetrack disguised as a jockey (the world's fattest jockey!). Harry squeezes himself into the jockeys' undersized telephone booth and receives a telephone call from Eliot to "give the money to Eliot Draisen". Eliot appears and takes the money, leaving Harry stuck in the booth. Nikki arrives and while struggling to get out of the phone booth, Harry tells her that he overheard the kidnappers' plans to fly to Buenos Aires. Making his getaway, Eliot tosses the "bug" out his car window to throw Detective Casey off his tail, then empties the suitcase of its cash and tosses it into a dumpster. Vince and Helen, who have been following Eliot, jump into the dumpster only to find the suitcase empty.

Eliot drives to the airport and telephones Helen, asking her to run away to Buenos Aires with him and the ransom money. She ditches Vince and rushes to Eliot. Once there, Helen confesses she was going to kill P.J. for the money, but now Eliot is rich and she is his. Vince appears with a pistol and Helen changes sides again. Eliot goes berserk, but Vince hits him in the head with the gun, drags him into a maintenance closet and chains him to a chair.

Harry and Nikki arrive at the airport but, forgetting he has a steel plate in his head, Harry is detained by security guards at the metal detector. As the plane taxis to the runway, Helen looks out to see Harry, on a boarding stair truck driven by Nikki, about to crash into the plane. Nikki loses control and hits a baggage cart, sending it into a power shed where Dwayne is holding Jennifer. The cart knocks Dwayne unconscious. Nikki crashes into the plane, throwing Harry through the plane's boarding door. Vince pulls his gun, but Harry, who claims to know aikido, accidentally kicks his shoes off and into Vince's face, knocking him unconscious.

Later, as Detective Casey gives Harry a reluctant apology, they hear Eliot Draisen kicking the closet door. Harry then confesses to Eliot about thinking that he would not solve the case, now that Jennifer is found. When Harry removes Eliot's gag, he angrily screams at Harry and inadvertently confesses to organizing the whole kidnapping and he cannot figure how a moron like Harry unearthed his kidnapping plan. A surprised Harry leaves the room and tells the nearby policemen to arrest and book Eliot.

Days later, Harry is made president of the company. He says goodbye to Nikki and P.J. Downing after his safe return of Jennifer. Nikki asks Harry if they could keep in touch should another case come up and Harry tells Nikki that he will let her know. After Nikki and her father leave, Harry sits down at his new desk in Eliot's former office. No sooner than he relaxes at his new position, Harry receives a telephone call from someone asking him to come to San Francisco to help solve a murder in a gay bar. Harry agrees to take the case.

(Note: Harry Crumb's sexual orientation is never revealed or discussed in the movie, but there are hints throughout that Harry might be a closeted homosexual because of his tastes in various fashions, his curly red hair, his lack of interest in women, etc.)

In the final scene, Harry, disguising himself as a drag queen (strongly resembling drag artist Divine), walks out of his office to head to San Francisco and stops to tell his secretary that this is going to be a rough case. As Harry leaves for San Francisco, the glass door of Crumb and Crumb Investigations shatters as a final gag as the end credits roll.