A very clever plot is let down by some bad writing.
Towards the end, two detectives go into the house of a murderer who we know to be extremely dangerous and very strong. They tell his wife to get out with the kids, then both climb down the stairs into a dark cellar. A moment later, the wife appears at the top of the stairs. Nobody seems to be worried about where the crazy killer might be or what he might do, except the viewer. This totally kills the mood of suspense. Even worse is the pay-off "bring spoons" (because the killer is arrested carrying ice cream). Wink.