spoiler since the disappearance at sea of her favorite niece phyllis murder mystery writer abigail mitchell and ruth gordon and have strong suspicion that it be phyllis husband edmund galvin and charles frank and who be responsible for her death . in fact abigail be convince that he murder her and make it look like a tragic accident . know that there no evidence to have edmund arrest for phyillis death and decide to take the law into her own hand abigail cook up this elaborate plan to do him in and make it look and like phyllis death and a tragic accident . get edmund to secretly come over to her mansion to give him the combination to her walk in safe and a she about to leave on vacation for new york city and abigail trick him into go inside lock the startle and surprise edmund in . with the safe be soundproof nobody at the mansion the butler maid and abigail personal secretary veronica and mariette hartley and hear him scream for help and the next day edmund be find suffocated to death . veronica discover edmund body a she be about to put away and for safe keep and abigail late murder mystery manuscript . lt. columbo and peter falk and be call on the case involve the strange death of edmund garvin to determine if it a murder or a tragic accident . go through edmund apartment columbo be puzzle to find out that he doesn not have a single photo of his late wife and who be miss for just a month . this tie into what abigail always felt about him in edmund not be in love with phyllis and also a suspect in her and in abigail mind and murder . columbo a big fan and together with his wife and of abigail murder mystery novel have a hard time realize that she in fact be responsible for edmund death . all the evidence point to abigil include a pair of miss car key that be edmunds . this all prove that abgail be in fact in the house and not on her way to the airport and when edmund be lock inside the walk in safe . go through all the evidence columbo come up with this strange conclusion that edmund must have leave some evidence inside the safe in write to who his killer be . that conclusion be quickly checkmate when it find out that edmund do not even have a pen or pencil as well a light and with the safe light bulb burn out and on him to write it . there also something very odd that inside the safe that have be on lt. columbo mind ever since he come on the case . this have to do with the black paint residue that be find under the dead edmund fingernail and on his belt buckle . it that evidence and when put together with a number of other item in the safe and that in the end hang edmund murder on the tricky and very cunning mystery writer abigail mitchell . edmund let abigail unknowingly convict herself in his final attempt a the air in the safe be be use up and by his breathing and in use burnt out matchstick to write on abigail last manuscript who murder him represent abigail mitchell .