The plotting is banal, the usual "husband is not who he pretends to be, and *possible spoiler* fakes his own death to escape being caught".
But the concept has rarely been executed better, and Goldie Hawn is simply outstanding here, with a truly fine supporting cast. The suspense builds logically from one step to the next, with an absolute minimum of contrivances. I was totally absorbed, especially as the "widow" slowly unraveled her husband's deceptions. Possibly the best scene in this movie was when she *possible spoiler* confronted her husband's pregnant new "wife". It was done superbly, with an absolute minimum of phony dramatics.
Too bad the ending couldn't have been done better, but, with the exception of those last five minutes, this film is well worth the effort of seeing.