John Huston's Heaven Knows, Mr. Allison (1957) stars Robert Mitchum and Deborah Kerr. And that's it. It's just Mitchum and Kerr through the whole movie, with the exception of some "Japanese" and American extras. Mitchum plays Mr. Allison, a marine who finds himself on a deserted island. He's spent days at sea and is exhausted but happy to be on land. He comes across Sister Angela (Deborah Kerr), a nun left behind by others and the sole inhabitant of the island. They stick together and battle to survive. So much time alone together leads to romantic feelings which Sister Angela must supress as she is about to take her vows. They contemplate whether they will be saved by the Americans, killed by the Japanese who keep returning to and abandoning the island, or if they will live for years and years, alone on the island.
The movie is filmed on location and not in a studio. Both actors are really in the elements and had to be very physical in their roles, especially Robert Mitchum. It doesn't surprise me that Mitchum and Kerr were chosen for this movie. I have always had the impression that neither of them were scared to get their hands dirty; no matter how elegant they might have appeared otherwise.
Lee Server's biography Robert Mitchum: "Baby, I Don't Care" has some really interesting behind-the-scenes information on this movie. Mitchum had been filming in Tobago for four months on the set of Fire Down Below (1957). He was relieved to be back home in America when his agent told him he had that he had to go back to Tobago to film Heaven Knows, Mr. Allison with John Huston. Initially he was thrilled to get such a good part, until he found out he was second pick after Marlon Brando, who had turned it down. Things weren't off to a good start.
The opening scene of the movie shows Mitchum in a raft. He's dirty, exhausted and sunburnt. The morning they shot that scene Mitchum had gotten drunk and din't want to come out of his tent. Director John Huston was not having it and to get back at Mitchum he put him on that raft for nearly 2 hours in the harsh sun. So any delirium you see on Mitchum's part in that scene, is authentic. Despite the initial feud, Huston and Mitchum got along very well after that.
Mitchum and Kerr hit it off too, although not romantically. Mitchum had much respect for Kerr, who could hold her own on set. Both had gotten sick with dengue and Mitchum had gotten hurt numerous times, putting his life in danger. Kerr was put in horrid conditions but never complained. Nothing like mutual suffering to bring two people closer together.
Also, because there was a Catholic nun in the story, the Legion of Decency had sent an inspector to Tobago to monitor shooting and to approve or disapprove of anything that went on with the storyline. At one point, Huston, Kerr and Mitchum had gotten so fed up with the inspector that they decided to pull a prank on him. They set up a fake scene in which Kerr and Mitchum grope each other and kiss passionately, all the while Kerr dressed in a nun's habit. Of course the inspector had a fit, much to everyone's amusement.