A novelisation of the screenplay was written by Howard Melvin Fast writing under the pseudonym "E. V. Cunningham".
Penelope Elcott (Natalie Wood) is the wife of wealthy banker James Elcott (Ian Bannen). Penelope decides to disguise herself as an old woman and rob her husband's bank. While the police, including Lieutenant Horatio Bixbee (Peter Falk), rush to get to the bank, Penelope escapes in a red wig and yellow suit. She donates some of the stolen money to a Salvation Army worker and donates the suit to a second-hand thrift shop. Con artists Sabada (Lila Kedrova) and Ducky (Lou Jacobi) immediately recognize the suit as an original designer outfit from Paris, and purchase it for a mere $7.
Penelope visits her psychiatrist, Gregory (Dick Shawn), and tells him all about her criminal activities. She says it began in college, when a professor (Jonathan Winters) lures her into his laboratory where he began his attempt to rape her, but she escapes, leaving her dress ripped off in the process. During the chase, she stole a diamond set watch of the Professor's. She next stole on her wedding day. When she caught her maid of honor Mildred Halliday (Norma Crane) kissing James, she swiped Mildred's earrings and necklace. Gregory suggests she is stealing to attract attention from her distant husband.
A young woman, Honeysuckle Rose, is accused of being the thief. Gregory wants to return the stolen money to the bank, but panics when he hears police cars arriving. Penelope confesses and tries to clear the innocent Honeysuckle, but Horatio the cop and husband James do not believe her. Ducky and Sabada pay a visit, trying to blackmail her, but Penelope foils their blackmail attempt.
Penelope hosts a dinner party, having stolen from all the invited guests. She tries to return the stolen items, but all claim that they have never seen them before. Penelope, confused and frightened, runs away. She again robs James' bank, but unlike the previous time, she is crying. James begs Horatio to find her. Penelope herself goes to Horatio with the stolen money, but the cop knows James would not press charges against his own wife.
The psychiatrist, Gregory, explains the dinner guests denied recognizing the stolen items because they would lose the fraudulently inflated insurance claims they collected. Gregory breaks down and begs Penelope to run away with him. She refuses, telling him she is cured. James realizes that he has neglected Penelope and starts seeing her face everywhere he turns. He goes to the psychiatrist's office, where James and Penelope happily reunite.Natalie Wood as Penelope Elcott
Ian Bannen as James B. Elcott
Dick Shawn as Dr. Gregory Mannix
Peter Falk as Lieutenant Horatio Bixbee
Lila Kedrova as Princess Sadaba
Lou Jacobi as Ducky
Jonathan Winters as Professor Klobb
Norma Crane as Mildred Halliday
Arthur Malet as Salvation Army Major Higgins
Jerome Cowan as Bank Manager
Arlene Golonka as Honeysuckle Rose
Amzie Strickland as Miss Serena
Bill Gunn as Sergeant Rothschild
Carl Ballantine as Boom Boom
Iggie Wolfington as Store Owner
The novel was published in 1965. The Los Angeles Times called it "that rare addition to whodunnit fiction, an original and unusual plot told with wit and intelligence."
Filming started in New York in May 1966.
Wood later said making the film was difficult for her. "I broke out in hives and suffered anguish that was very real pain every day we shot," she recalled. "Arthur Hiller, the director, kept saying, 'Natalie, I think you're resisting this film,' while I rolled around the floor in agony."
The film was a box office disappointment. Wood did not make another movie for three years.