Kitty Kidd, better known as Ada Mason, is the secondary antagonist of the Hercule Poirot novel The Mystery of the Blue Train and its subsequent televised adaptation in the British television mystery show Agatha Christie's Poirot, as its tenth series' premiere. Mason is a housemaid who was widely known as an actress skilled in male impersonation, which was employed by jewelry thief and murderer Richard Knighton to make her an accomplice.
She was portrayed by Bronagh Gallagher in the television adaptation.
Biography[]
Mason worked with Knighton for a long time when they met at some unspecified point after his early jewel heists, starting at a villa where he stayed as a wounded soldier. Mason would join Knighton in scouting for marks and conning their victims before heisting them, eventually coming across American oil magnate Rufus Van Aldin, whose daughter Ruth wore a highly valuable ruby on a pendant named the Heart of Fire.
Mason and Knighton worked together to gain employment under Van Aldin, Mason as Ruth's personal maid, Knighton as an Aldin's secretary. Ruth was taking Le Train Bleu in Mason's company, in the novel to meet her lover, in the film to meet her mother Van Aldin had placed in a convent Knighton snuck aboard the train and had Mason let her into the cabin. In the novel Knighton strangled Ruth to death, while in the film, Knighton bludgeoned Ruth to death with a hammer, her face almost completely destroyed. Knighton jumped off the train at some point, while Mason, with her skills in disguise, pretended to be Ruth while she was dead to throw off the investigation, as well as make an alibi for herself for leaving and rejoining the train with and without her disguises.
Mason and Knighton covered for each other, with fake alibis Knighton seeing her at the hotel but Mason not seeing him. Mason became jealous when Knighton started to fall in love with Katherine Grey, the cousin of the villa's owner where Knighton had stayed and heisted previously. She barged in between the two of them at the villa party, smashing glasses and a bottle seemingly by accident, but Knighton sent her off to Van Aldin to shoo her away. Needing to divert suspicion, Mason pretends to sob from "recalling" Ruth's abusive and indebted, gambling husband Derek Kettering being at Ruth's cabin, leading to his arrest.
However, in the film, the covers dissolve when Mason, garbed in dark clothing concealing her, breaks into the villa and tries to stab Katherine in her sleep. She ducks and hides under the bed, while Katherine's cousin Lenox pounces Mason and bites her neck, making her flee out the window. Poirot then connects Knighton to the jewels, as he was one soldier in the villa when the owner, Rosalie Tampin, was taking in war vets, and Poirot saw an article of one of Rosalie's jewels stolen there at the time. Realizing Knighton and Mason both made fake alibis because they were in collusion. He gathers the suspects on the train. He reveals Mason's bite mark, then reveals Knighton as the murderer.
In the novel, both conspirators surrender to police. Knighton holds a razor blade on Katherine in the film and tries to escape, with Mason charging police and getting arrested to by Knighton time. Much to her devastation, Knighton sees no escape and commits suicide by jumping in front of a train, leaving the ruby in Katherine's hand.
