Michael is working as a chauffeur but wants to get ahead in life despite his poor background and the heavy hand of his highly religious mother, who tells him that God is forever watching on his actions. He meets Ellie, an heiress and the two fall in love, marry, and build the home of their dreams at Gypsy's Acre designed by Michael's ailing friend Santonix, to the consternation of the locals and her family - and then there is a tragedy.
Endless Night is Agatha's great later novels, which is more psychological based and doesn't feature Poriot or Marple - however in this TV adaptation starring Julie Mackenzie as the sleuthing spinster Miss Marple features as an observer of the sinister undercurrents unravelling. I agree this shouldn't have been Marple-ised, and it would have been better alone. But it's still a compelling watch, with great performances all around, including Julie Mackenzie. An interesting trivia is that Endless Night was based on a short story -the case of the caretaker - Agatha had published in the Strand magazine and it did feature Miss Marple.