I sent an email to ITV (itvihelp@itv.com) inquiring about which season "The Mysterious Affair at Styles" originally aired in, and the response I received confirmed that it belongs to the third season. ITV suggested that the error in categorization might be due to the fact that "The Mysterious Affair at Styles" originally aired in the same year as Season 2, which could have led to the incorrect classification.

Now, the web archive of the Agatha Christie Limited company (provided by @Reiver) and ITV, which originally aired the series, both indicate that "The Mysterious Affair at Styles" belongs to Season 3. It is time to correct this error.

Here are the original texts of my email and the response, with names replaced by "NAME":

Dear ITV Team,

I hope this message finds you well.

I am a dedicated fan of Agatha Christie's Poirot series, and I have recently encountered some confusion regarding the episode "The Mysterious Affair at Styles." While browsing different sources, I noticed that TMDB (The Movie Database) categorizes this episode as part of Season 3, whereas other websites list it under Season 2.

Could you please confirm which season "The Mysterious Affair at Styles" originally aired in? Your assistance in resolving this discrepancy would be greatly appreciated.

Thank you for your time and help.

Best regards,

NAME

2024.08.21

Dear NAME,

Thank you for your email.

Regarding "The Mysterious Affair at Styles" the answer you are looking for is that it was part of season 3 as a feature length to celebrate the centenary of the author's birth, subsequently its year of release aligned with season 2 which may be the cause of some confusion, however it was definitely a part of season 3. I hope this helps!.

Kind regards,

NAME

ITV Customer & Viewer Services