At the private island retreat of wealthy industrialist George Stark, a group of people have assembled for a weekend getaway; among the guests is scientist Professor Gerry Farrell.

As Stark, Nick and Jack badger Farrell for the formula—the original documents for which he has secretly destroyed—by offering him cheques for $1 million each from their Swiss bank accounts, Jill discovers the dead body of Charles on the beach.

Stark offers Trudy his cheque for Farrell's formula, which she reveals still exists on a microfilm, and uncovers a previously hidden motorboat which can take them to the mainland.

Aware of his inescapable fate and thankful to her, Farrell gives Isabel the number, and she happily leaves, instructing her chauffeur to drive her to Lausanne.

Produzioni Atlas Consorziate purchased Mario di Nardo's script for Five Dolls for an August Moon with plans to make it into a vehicle for actress Edwige Fenech, though early publicity instead spotlighted Princess Ira von Fürstenberg (who was one of the film's principal investors).

[1] Bava was very reluctant to take on the project, since he felt the script was a poorly written ripoff of Agatha Christie's novel And Then There Were None (1939), but agreed to do it under the condition that he be paid up front.

[1] However, in addition to insisting on the use of his usual camera crew (headed by Antonio Rinaldi), Bava made two significant changes to the film's script: putting the corpses in polythene bags inside a walk-in freezer (di Nardo's script put them in underground graves with cross-shaped headstones) and adding on the twist ending with Farrell and Isabel.

[1] Five Dolls for an August Moon was one of Bava's most obscure films, and did not receive an official American release until 2001 when Image Entertainment distributed it on DVD.

After the Image disc went out of print, Anchor Bay Entertainment re-released the film as part of the Mario Bava Collection Volume 2 box set on 23 October 2007.

Butler placed the blame for the film's failure primarily on the script, and commended Bava for managing to inject some visual interest into the weak material.

[2] In his review of the 2013 American Blu-ray release for Slant Magazine, Budd Wilkins wrote, "Five Dolls for an August Moon isn't top-tier Bava by any means, but for those with eyes to see, there are pleasures aplenty to be gleaned from this playfully abstract jeu d'esprit.