More often than is acceptable, a film's death is delivered with the words "Adapted from the play by...." In the hands of most directors, stories don't make the jump from theater to cinema without coming off like nails on a chalkboard.
It's not that it can't be done well, but the differing needs of actors and directors between the two mediums require a director with intimate knowledge of both. Luckily, Kenneth Branagh is one of those rare few, and his remake of the 1972 film Sleuth represents that theater/cinema crossover at its finest.
Both the 1972 film and Branagh's remake are adapted from a play by Anthony Shaffer, both feature Michael Caine, and both delve into the cruelty that humans can inflict upon each other.
Caine plays Andrew Wyke, a fabulously wealthy, aging crime novelist who's holed up in a massive, state-of-the art palace in the English countryside. Jude Law plays Milo Tindle, an out-of-work actor (or hairdresser, or chauffeur; it's not really clear) who happens to be schtupping Wyke's estranged wife.
(Mercury Fun Fact™! In the original version, Caine played Tindle, making this at least the second time Caine has appeared in a remake of one of his older films. The other one was Get Carter!)
(Bonus Mercury Fun Fact™! This marks the second film in which Jude Law has played a character that Caine first played. The first was Alfie!)
The setup of the film—that Tindle wants Wyke to give his wife, Maggie, a divorce so they can get married, but Wyke refuses—is little more than a canvas for Branagh and Pinter to paint a dark, disturbing, and humorous portrait of human psychopathology.
Tindle and Wyke's motives are slowly revealed through skillfully crafted, hilariously cutting dialogue, to the point where each is attempting to destroy the other through sheer humiliation. Their interaction escalates, with each character taking their "game" to a new, horrifying level at every turn. At first, it seems torturous and cruel (which it is) until about mid-way through, when it becomes obvious that both characters actually like being debased. And then there's the final third of the film, which is among the most genuinely uncomfortable pieces of film I've ever seen—in other words, Sleuth comes highly recommended.