"Perry Mason" was a one-hour television program which ran on the CBS television network from 1957 to 1966. Perry Mason (Raymond Burr) is a Los Angeles criminal defense attorney who specializes in defending people accused of murder. He is assisted by his secretary Della Street (Barbara Hale), and private investigator Paul Drake (William Hopper). The district attorney who prosecutes the cases is Hamilton Burger (William Talman) who is assisted by police lieutenant Arthur Tragg (Ray Collins). Some stories were adapted from mystery novels written by Erle Stanley Gardner and others were written for the program. The program followed a formula where Perry's clients are always innocent, and the "real killer" confesses at the end.

This episode is titled "The Case of the Grinning Gorilla" and was first broadcast on April 29, 1965. Perry Mason and his assistants Della Street and Paul Drake find themselves at the mansion of an eccentric millionaire who keeps monkeys, chimpanzees, and a gorilla. The gorilla is played by actor and stuntman Janos Prohaska. At one point Perry and a former employee encounter the gorilla and the employee tells Perry to put some coins in front of the gorilla for the animal to play with. Some US coins are shown lying on a carpet.

Perry Mason (Raymond Burr) and Della Street (Barbara Hale) are at an auction of unclaimed packages and Della purchases one for $5.00.

Della takes her package back to Perry's office and opens it. She finds a photograph album and a diary written by a Helen Cadmus (Charlene Holt) who supposedly disappeared from a yacht belonging to eccentric millionaire Benjamin Addicks (Harvey Stevens). Addicks lives in a mansion in the country near Los Angeles where he keeps exotic animals. A man named Nathon Fallon (Victor Buono) appears in Perry's office.

Nathon offers a great deal of money for the girl's papers. Perry and Della have become curious about the girl and refuse the offer. Perry finds out that Nathon and a Mortimer Hershey (Gavin Mac Leod) are employees of Mr. Atticks. Perry visit's a restaurant to meet Paul Drake (William Hopper), a friend of Perry's and a private investigator. Paul introduces Perry to Josephine Kempton (Lurene Tuttle) who used to work for Addicks until she was accused of stealing jewelry and fired for theft.

Mrs. Kempton claims that she did not take anything from Atticks house. Perry and Della make an appointment to visit Mr. Atticks.

While Della looks around the house Perry talks to Addicks who is heavily bandaged due to an altercation with his gorilla. Della dips over a large urn and finds the jewelry that Mrs. Kempton supposedly stole. It is implied that a chimpanzee left the jewels there. Perry and Della leave and Perry later returns with Mrs. Kempton, who has a key to a back entrance. Perry enters the house and is followed by the gorilla.

Perry enters a room and locks the door.

Perry finds the body of Mr. Addicks and the still-living Mrs. Kempton. The gorilla breaks down the door.

Mrs. Kempton tells Perry what he should do to calm down the gorilla.

Mrs. Kempton tells Perry to get close to the ground and to put some coins in front of the gorilla as he likes to play with coins.

A close-up shows the US coin denominations.

The coins appear to be (from the top left): A Roosevelt dime, a Roosevelt dime, a Lincoln cent, a foreign coin, a Jefferson nickel, a Washington quarter, and a cigarette lighter. Paul Drake has found Helen Cadmus alive at a motel.

She married Mr. Atticks and he has kept her out of sight as he believes that two of his employees are plotting against him. Paul brings Helen to the Atticks' mansion and a number of people are there.

Perry explains that two of Atticks' employees, Nathon Fallon and Mortimer Hershey, were sending money from Mr. Atticks to a fictitious relative and when Atticks married Helen he disrupted their scheme and that they had to kill him.

As Atticks' wife she inherits his money and his monkeys.

Victor Buono as Nathon Fallon
Charlene Holt as Helen Cadmus
Robert Colbert as F. A. Snell
Lurene Tuttle as Josephine Kempton
Gavin Mac Leod as Mortimer Hershey
Bartlett Robinson as Sydney Hardwick
Director: Jesse Hibbs
Writers: Erle Stanley Gardner, Jackson Gillis
Based on Erle Stanley Gardner's 1958 novel with the same title