Calling a Legion meeting, Poirot exposes one of its members, Franklin Clarke, as the A.B.C. murderer. His motive was simple – Lady Clarke is slowly dying from cancer, and upon her death, Carmichael would probably marry his assistant. Franklin feared a possible second marriage, as he wants all of his brother's wealth, so he chose to murder his brother while Lady Clarke was still alive. A chance encounter with Cust at a pub gave Franklin the idea for the murder plot – he would disguise his crime as being part of a serial killing. Having created the letters Poirot would receive, Franklin set up Cust with his job, giving him the typewriter and other items Franklin would use to frame him for the murders. A suggestion by Hastings makes clear that the third letter was misaddressed intentionally, because Franklin wanted no chance of the police interrupting that murder. Franklin then followed Cust to the cinema, committed the last murder, and planted the knife on him as he left.