There's Still Hope For These Dead Game of Thrones Characters — in the Books

How he dies on the show: In season five, Ser Meryn is sent to Braavos, where he is recognized by Arya. Disguised with a different face, Arya meets Ser Meryn in a brothel, where she knows he likes to abuse young girls. Once alone with him, Arya reveals her true face and stabs him in the eyes before slitting his throat.

Where he's last seen in the books: In the novels, Ser Meryn is never sent to Braavos and remains at the Red Keep, often guarding the apartments of the Hand of the King.