S09E02 - Murder in Mesopotamia

Dr. Leidner is a Swedish-American archaelogist on a dig in Iraq, then a British protectorate. His wife was previously married to a Frederick Bosner, a young man who worked for the U.S. State Department but was actually a spy for Germany during the World War I. He was caught, tried and sentenced to death. He managed to escape while he was being transported, but it was to no apparent avail as he ended up on a train that crashed, and a body bearing his identification was found in the wreckage.

Amy Leatheran is a nurse traveling in Iraq when she meets Dr. Leidner, who asks her to join the dig to look after his wife. Mrs. Leidner has been frightened by weird goings on, such as a ghostly face appearing just outside her window and has received threatening letters. Mrs. Leidner confides to Nurse Leatheran that she had received similar threatening letters several years before that were supposedly from her dead first husband. They arrived every time she would go out with a new man, then stopped when she broke off the relationship. One of the letters was signed with her late husband's name, but she had no letters from him - they had been married only a short time - so she could not ascertain whether the letters were genuine. No letters arrived when she met and then married Dr. Leidner, so Mrs. Leidner had assumed they were written by some crackpot who had either died or given up keeping an eye on her.

Then Mrs. Leidner is found dead by her husband in her room, struck fatally on the head with a large blunt object. The Belgian detective, Hercule Poirot, is also travelling in Iraq and his old friend, Dr. Reilly - a physician acquainted with the dig - asks him to solve the crime.