Lebel does everything he can to discover the Jackal's identity. He first calls upon his "old boy network" of foreign intelligence and police contacts to inquire if they have any records of a top-class political assassin. Most of the inquiries are fruitless, but in the United Kingdom, the inquiry is eventually passed on to the Special Branch of Scotland Yard, and another veteran detective, Superintendent Bryn Thomas.
A search through Special Branch's records turns up nothing. However, one of Thomas's subordinates suggests that if the assassin were an Englishman, but primarily operated abroad, he would most probably come to the attention of the Secret Intelligence Service. Thomas makes an informal inquiry with a friend of his on the SIS's staff, who mentions hearing a rumour from an officer stationed in the Dominican Republic at the time of President Trujillo's assassination. The rumour states that a hired assassin stopped Trujillo's car with a rifle shot, allowing a gang of partisans to finish him off. Additionally, Thomas also learns that the assassin was an Englishman, whom he is able to identify as Charles Calthrop (...)
Checking out the name of Charles Calthrop, Thomas finds a match to a man living in London, said to be on holiday. While Thomas confirms that this Calthrop was in the Dominican Republic at the time of Trujillo's death, he does not feel it is enough to inform Lebel, until one of his junior detectives realises that the first three letters of his Christian name and surname form the French word for Jackal, Chacal (...) the Special Branch raids Calthrop's flat, finding his passport, and deduce that he must be travelling on a false one (...)
[Epilogue] In London, the Special Branch are cleaning up Calthrop's apartment when the real Charles Calthrop storms in and demands to know what they are doing. Once it is established that Calthrop really has been on holiday in Scotland and has no connection whatsoever with the Jackal, the British are left to wonder "If the Jackal wasn't Calthrop, then who the hell was he?"
