Endless Night (1972)

Endless Night is a Christie, but not really a murder mystery. It's actually more of a psycho drama, but its inclusion on a horror films site is assured by some determinedly spooky set pieces. There are several scenes which linger in the mind long after the film has finished, and it may well have been seen by a lot of you on some late night TV slot and then been half forgotten.
The film starts with one of them, a weird dream sequence involving a woman with a blank face. Enter Hywell Bennet as our fresh faced narrator. He's in Christie's (clever, eh?) bidding on an expensive painting. Luckily, he doesn't get it (he's a penniless chauffeur) but he does display a remarkably original view on auctions which every Ebayer should take to heart:
"Between my bid and the next, I owned that picture..." ("No you didn't!" explains the rest of the world, patiently)
On a driving job in Europe, he meets with an architect and explains his lifelong dream - to build a house in a place called Gypsy's Acre. After being approached by someone (or something) in an art gallery, our baby faced hero develops an attitude problem, travels down to Gypsy's Acre and meets an American girl called Ellie (Hayley Mills, playing against type as a sweet and innocent blonde popsy without a worldy bone in her body). After explaining to her about his dream house (he just won't bloody shut up about it) they meet a spooky old woman and her cats, who intimates that something horrible has happened in the past, and more horrible things will occur.
This is breezily brushed off by Bennett with the immortal line "Nutcase. We breed 'em in England".
As if that wasn't enough, it turns out that Ellie is the "sixth richest girl in the world" and the two marry and build Bennett's dream house on Gypsy's Acre.
The plot wastes no time in introducing several more shady characters, the most important of which is Britt Ekland (also playing against type, as an annoying bint with an impenetrable middle European accent), who is Ellie's best friend Greta. (Greta is basically Ekland's character Lucy from Asylum - a not-very-nice girl who seems to rule Ellie with a rod of iron)
The others are Peter Bowles as a caddish uncle (natch) and his wife Miss Moneypenny.
As rocks get chucked at the window and a murder appears to take place, without the help of any Belgian detectives it's left to the audience to sort it out.
Who is the murderer? According to the cinema posters, only one in 10 people get it right. Filmgoers must have been stupider back in the 70s, but Endless Night is still an entertaining hour and a half.
The temptation with any film that has the word "endless" in its title is to be cruel, but the truth is it's not a bad little movie, especially for Bennett and Mills' excellent taste in James Bond-style 70s pads, complete with swimming pool under the sliding floor.