This was a character study in the truest sense of the word, and the destruction of a family through their inability to come together in the aftermath of tragedy.
First let me say that I've never been a fan of Donald Sutherland. I find him unattractive, his voice irritating, and he's played so many nutjobs that I was put off immediately when he came on screen, waiting for him to finally snap or start giggling maniacally.
Second, let me say that I've enjoyed and admired Mary Tyler Moore for years. I went into this movie expecting to like her. I understand this was a first dramatic role for her.
Finally, I was very unfamiliar with Timothy Hutton, so I had no preconceived notions or expectations.
Their performances turned my expectations on their ears. Hutton was brilliant as the tormented survivor of the boat accident in which his older brother died. Sutherland was touching in his portrayal of a father scrambling to hold the remnants of his family together. Moore was infuriating as a mother who, in losing her elder son, found it impossible to connect with her younger son. I kept waiting for her to scream "it should have been you!"
I think Moore's character was the least served. It would have been helpful for a better look inside her pain, to understand her distance. Judd Hirsch as the psychiatrist should have taken a crack at her. He did wonders for Hutton's character.
Finally, a note for Dinah Manoff, who I knew best as Carol Weston in several spin-off tv series, starting with Empty Nest. She was only in the movie for one scene, but had a lasting impact on Hutton's character and was the impetus for a climactic scene. In fact, Manoff's scene stands out most strongly to me.
All in all, I'd say it's a very good movie.