Bunny Lake is Missing is disappointing, and only because most of it is so good. The premise is that an American woman, Annie Lake (Carol Lynley), moves to England and one day she eaves her daughter at pre-school only for her to disappear without a trace. Or did she leave her there to begin with?
The film is a maze of possibilities, and I found I didn't really have any one idea of what was going on. You cannot take anything for granted. Laurence Olivier plays a police superintendent taking charge of the case, and while in some part he seems to share the audience's sense of bewilderment he's also fairly enigmatic in and of himself, which only adds to the feeling of hysteria.
Carol Lynley, though her line delivery can be stiff, won me over. She does play a convincingly hysteric mother, to just the right degree at which you wonder if she might be a little bit too hysteric. Keir Dullea of 2001: A Space Odyssey fame, however, is undoubtedly excellent. He's instantly believable right from the first scene as Annie's controlling brother. Martita Hunt was a stand-out, and Noel Coward was outstandingly creepy, only he doesn't overplay the creepiness, either. He embodies creepy in a quirky vein.
The bulk of the film is really good. I'll agree with senorroboto in some part and say that the build-up might be slow for some (I tend to like slow build-up as long as it builds to something worth the wait), but I'm not sure if I feel the same way about the ending. I've read a fair bit of praise for the ending, but I'll explain to you who've seen it why it didn't work for me. Don't read on if you haven't seen the movie yet, because I definitely think it's worth keeping yourself in suspense. Now, then:
I like the conceit of the twist and the ending, even though Steven is obviously the culprit as he has no other clear role in the story (something that would've been less forgivable if the film didn't have such an unusual angle to its mystery). Steven as a regressive nutcase who wants to eliminate Bunny because of his psycho-sexual fixation on his sister is interesting, but the climax of the film bungles it. The script paints the concept in such an exploitative and cartoonish light. I suppose the idea of Annie playing childhood games with Steven to distract him could work in some capacity, and I like that, for much of it, you can't totally tell if Annie's a nut job, too. Sadly, in its specifics, and in how it's executed, it becomes unbelievable. So, Annie and Steven have a happy childhood and she only now learns that he's a murderous psychopath? If the nature of his mental state weren't portrayed in such an exaggerated way I think you could buy him as a successful, wealthy person, as he appears to be. I think, if you tone down the stupid regressive child mind stuff and play Steven more as a possessive sociopath it would be, as far as I'm concerned, a lot easier to buy. I'm not sure what you do with the finale in that case (I'm brainstorming ideas as I type), but surely something else could do.
And the finale is unbelievable in more ways than one. The sound editing team must've been flummoxed by this project, because in the numerous instances in which Annie sneaks around Stevens house without him hearing her the sound is either very clearly brought down in post (forgive me, but the technical terms aren't exactly within my repertoire), or covered up with loud non-diegetic music. In a mystery/thriller, you cannot afford to have the illusion shattered. It deflates tension, and tension is the KEY to an interesting story, in any genre, really, but especially in mystery and thriller. Why, thiller is hardly even a genre. It basically just tells you that the movie has a lot of tension. Add to that Steven's fairly stupid plan and you have a climax that, while promising, isn't really worth the wait.
Also, one other spoiler I should stick in here: The production couldn't find ONE kid with an American accent to play Bunny, a character who is specifically stated to speak with an American accent? They couldn't cut here ONE line? Honestly, people.
So, there it is. Like I said, most of what's here is very good, and this could be a thriller of great stature if you tweaked a few things. Even that aside, it's still pretty good. If you, like me, find a little mindbending thrill to be a good time, it's for you.