[2] Illya Kuryakin is investigating the theft of cats in the Soho area of London, and Napoleon Solo is on a mission to determine the whereabouts of the famous, suddenly youthful appearing, and now missing 83-year-old biologist Benjamin Lancer.

Solo contacts Lancer's daughter Lorelei, a model at the Paris salon of Madame Raine De Sala.

De Sala herself visits Sir Norman Swickert, a very old statesman she knew and admired as a child, and brings along with her Dr. Gritsky – a colleague of Dr. Lancer.

Swickert becomes convinced that the middle-aged Bainbridge is actually the elderly Lancer made young again via a medical process.

Swickert refuses to say much beyond that Lancer was a member of the Bridge of Lions club, a private chess club that Swickert founded to build a bridge among the great men of many nations to allow them freedom to communicate under all circumstances – thereby reducing the chances of cataclysms like World War I.

Shortly after leaving Swickert's home, Solo's car crashes as a result of sabotage – implied to be the work of Olga.

Solo (none the worse for his auto accident, which is never discussed) arrives as well and, after comparing notes the two men reach the conclusion that the cats, having a similar nervous system to humans, are being experimented upon with the de-aging process developed by Lancer and Gritsky.

Kuryakin finds that hat associated with the pin and it turns out to be from Madame Raine De Sala's salon.

Solo and Kuryakin return to New York, and since the secret of the de-aging process is written in code, it appears to be lost to science for a very long time.

The character remained named Wanda and, other than the replacement of the actress, the role was essentially unchanged from the television episode.

Also new were scenes dealing with the death of Lorelei Lancer; whereas in the episodes she was strangled off screen, in the film her dead body is shown staring open-eyed from the bottom of a tub filled with water.

Also, the film had a new score composed for it by Gerald Fried, because "The Bridge of Lions Affair" had been tracked with music from other episodes.