Gig Young...
...Is so hilarious in this movie! I love his line delivery, the "business" he does with all the paraphernalia when he's barbecuing. But I especially love his first scene in the bathroom with Anne Jackson--as he is sitting on the toilet lid and pulling her onto his lap, he says with great sincerity "Sordid? How could you call this sordid?". And then he goes on to explain in great detail how he "...doesn't want to hurt anybody"--very funny stuff.
Gig had another great role in the '70s in "They Shoot Horses, Don't They?", and he won the Best Supporting Actor Oscar for that one. He went out on a couple of fine performances before taking his own life. Good actor.