This is a good series which misrepresents its origins. Episode 1 part 2&2 is represented as an Agatha Christie story but only has taken bits and pieces. The title is the same. The names of the main characters are the same, but only the names and not the characters really. Yes, it happens all the time when an author loses the rights by selling them they also lose any say in how the story might be reproduced in film, television, or other means. In this rendition of "A Secret Adversary" so much has been rewritten it is no longer a story by Agatha Christie but only a story claiming to be "based on". "A Secret Adversary" is Christie's debut Tommy and Tuppance who are friends, not married, and decide to join forces as crime solvers. It's a complex story set between WWI and WWII. A pre-Nazi force threatened England with a revolution. In this version Tommy is not the suave smart and funny man who works with Tuppance but a whimpy milquetoast.