Hilary Hammond was in the audience where a murder happened. According to Charlotte Pollard, he was average in attractiveness. He took her away from the music hall. He was a shipping clerk and knew where the "house of the Scraggly Witch" was — it was a bay in Dumfrieshire. He helped Charley to get there. He noticed that she was quite adventurous. They were supposed to be married, and he was upset when they didn't.
It turned out that he was the one who committed the murder. He was a spy for the Germans, and the murdered man was the key to telling all the members of the gang the information. He wanted to take the TARDIS to Berlin.