Penelope Elcott [Natalie Wood] is married to James Elcott [Ian Bannen], a wealthy banker, and she feels a restlessness behind her comfortable life. One impulsive morning, she quietly decides to disguise herself as an old woman and rob her husband’s bank, kicking off a bold sequence of events. As alarms blare and police close in, including Lt. Horatio Bixbee [Peter Falk], Penelope makes a swift escape in a striking red wig and a bright yellow suit. In the aftermath, she donates some of the stolen money to a Salvation Army worker and hands the suit over to a thrift shop. The ensemble doesn’t stay hidden for long: con artists Sabada [Lila Kedrova] and Ducky [Lou Jacobi] recognize the outfit as a Parisian designer original and purchase it for a mere $7, instantly tying fashion to mischief.
To make sense of her actions, Penelope sees her psychiatrist, Dr. Gregory Mannix [Dick Shawn], and recounts the life of her “crimes.” She explains that the pattern began in college, when a professor [Jonathan Winters] in his laboratory attempted to assault her, a terrifying moment that she escaped from, leaving her dress torn in the process. During the chase that followed, she swiped the professor’s watch fob. The next breach came on her wedding day, followed by a theft from her maid of honor Mildred Halliday [Norma Crane]—her earrings and necklace disappearing in a flash. Gregory suggests that the thrill of stealing is a response to wanting more attention from a husband who seems distant.
A fresh accusation arises when Honeysuckle Rose [Arlene Golonka], a young woman, is pegged as the thief. Gregory contemplates returning the stolen money to the bank, but panic erupts as police vehicles arrive. Penelope confesses in a bid to clear Honeysuckle, yet Lt. Bixbee and James refuse to believe her innocence, casting doubt on her tale. The danger escalates when Sabada and Ducky press their blackmail, only to see Penelope outwit them and keep control of the situation.
Penelope then stages a dinner party, a gathering at which she finds herself having stolen from every invited guest. She attempts to return the pilfered items, but the guests insist they have never seen them before, leaving her increasingly unsettled. In another turn of risk, she robs James’s bank once more, this time with tears in her eyes. James pleads with Horatio to locate her, torn between concern and loyalty.
The psychiatrist later reveals the cruel logic behind the guests’ denial: they have been colluding to swell fraudulent insurance claims. Gregory—even in his own admission—breaks down, begging Penelope to run away with him. Yet she refuses, insisting that she has been “cured.” James, meanwhile, comes to realize how deeply he has neglected Penelope; he starts seeing her face everywhere he turns. He visits the psychiatrist’s office, where a quiet moment of recognition unfolds. In the end, James and Penelope share a reunion, choosing to face their renewed bond together.
