The Grass Is Greener (1960), produced and directed by Stanley Donen.
This light comedy of infidelity did not do well in the US, probably because audiences wanted to see more jealous outrage and punches thrown rather than Cary Grant's dry drawing-room wit and cool calculation. Adapted from a stage play so it is dialogue-heavy.
It is notable for gathering together four great stars who had worked together in pairs previously:
Robert Mitchum and Deborah Kerr:Heaven Knows, Mr. Allison (1957), The Sundowners (1960).
Robert Mitchum and Jean Simmons: Angel Face (1953), She Couldn't Say No (1954).
Cary Grant and Deborah Kerr: Dream Wife (1953), An Affair to Remember (1957).
Deborah Kerr and Jean Simmons: Black Narcissus (1947), Young Bess (1953).
Available on Blu-ray from Olive; no subtitles.