[TOMT] TV show episode where a woman was murdered by her boyfriend's mother/grandmother through a locked hotel room door
Drama/detective TV show where one episode's synopsis is an older murder case being reopened because the convicted murderer (i'm gonna call him John) requests it (?). The victim is John's girlfriend that got killed in a hotel room locked from the inside where they spent the night together and obviously he was the only suspect for the murder.
In the end it's revealed that the murderer was John's mother/grandmother who got into the locked room with a string and newspapers that helped her get the key from the other side of the doors. She confesses in some way to the detective and when they ask for proof she reveals a vial with the girfriend's blood in it which she keeps in her purse. She murdered the girlfriend to give a lesson to John or some kind of revenge, and when he's spent enough time in jail she'd confess to the murder herself.
That's all I can remember, thanks to anyone reading and responding