Haigh happened across Archibald and Rose Henderson just as they were selling their house. While not as wealthy as the McSwan's, Haigh decided to cultivate their friendship as a precursor to his ultimate plan to dispose of them and claim their property as his own.
At first posing as an interested buyer prepared to offer more money than the house was worth, the charming Haigh this time then used a mutual love of music to ingratiate himself with the unsuspecting couple and during their long, unguarded conversations discovered more about their property interests.
Luring the Archibald to the address on the pretext of showing him an invention, Christie shot him dead. Later that day, he brought Rose to the house and disposed of her in a similar fashion. Again he would claim to have drunk their blood before putting them in lidless drums with sulphuric acid.
This time, he was not as thorough as he had been during his previous crimes and despite the fact that Mrs. Henderson's foot was still intact, he disposed of the remains in the corner of the yard. Like many serial killers before and since, the failure of any investigation to even touch him had begun to make him feel invulnerable.
Again, he began the lengthy and difficult process of convincing the Henderson's family that their absence was legitimate, and that he was the rightful recipient of their property. Unlike the McSwan's, he faced immediate and deep scepticism from Rose's brother Burlin, who was prepared to go the police to report the couple as missing.
Forging letters to other relatives and spinning a tale of how Mr. Henderson had fled to South Africa following an illegal abortion operation he had performed, Haigh just about managed to pull off his crime and found himself with a handsome £8000 dividend from his crime.
Despite this, his taste for high living and gambling saw him running out of money by the summer. While living in the upmarket Onslow Court Hotel in South Kensington he had acquainted himself with a wealthy woman who was also a guest - Mrs. Durand-Deacon. His thoughts soon turned to murder and acquisition, but the time proved to be a frustrating one for Haigh in other ways.
Barbara Stephens, his girlfriend of the time became suspicious when he tried to make an insurance claim on a crashed car and Burlin Henderson once again appeared on the scene, talking about getting an investigation into his missing sister and brother-in-law. So concerned was he that he wanted to take the matter up at Scotland Yard and wished Haigh to come with him.