The Minx (1969)

Ruthless, power-hungry Henry Baxter, president of Lawson Industries, makes plans for the corporate takeover of Benjamin Thayer's company, Eastern Devices, by covertly purchasing its stock through a Swiss bank. In order to remove Thayer as chairman of the board of Eastern Devices, Baxter must obtain the support of two board members to vote their proxies with his. Baxter arranges a weekend party at his hunting lodge for the two reluctant board members, and Baxter's brother-in-law, John Lawson, is told to provide women for the party. Unknown to Baxter, Lawson is secretly in league with Benjamin Thayer, and the women provided for the party (Terry, Nicole, and Susan) are experts in corporate spying and blackmail. Baxter needs the signature of his wife Louise, an older woman he married to gain control of Lawson Industries, on some essential documents; he persuades her to sign by making love to her. He then demands a divorce. She refuses and hires private detective Sam Burke to gather evidence that would make the separation impossible.