Archibald (The Unicorn and the Wasp)
Talk about it here.
Sometime before December 1926, Agatha Christie's husband, Archibald, began having an affair with another woman who Agatha described as being younger and prettier. This broke her heart, but social attitudes at the time demanded her to "carry on".
According to The Enquirer, Agatha went missing following an exchange of words with her husband. Archibald was interviewed by Surrey Constabulary, along with the rest of Agatha's family and friends regarding the disappearance. She would not be seen again until she surfaced in Harrogate over eleven days later.