It's the lynchpin of the Houdini murder conspiracy. The story goes that in final days of Houdini's life, when he was showing improvement, a shadowy outsider, sometimes identified as Dr. George Lefevre, came in and administered a mysterious serum. This caused Houdini's relapse and death. Clearly murder!
Hollywood is a chief offender here, with The Travel Channel's Mysteries at the Museum literally reenacting the scene with a mysterious black clad figure creeping into Houdini's room with a syringe. Watch out Harry! He looks French Canadian!
But here's an article that ran 96 years ago today that injects a little reality into the story of the mystery serum.
This article shows that the serum was administered by Houdini's own doctors right after his operation. It was not administered by an outsider and not in the final days. Furthermore, this article states that Dr. George Lefevre was not even in Detroit when the serum was used. He came later in the week to report on the serum's effects.
It is true that the serum was experimental and we don't know what was in it. But I expect it was a cocktail of ingredients believed to fight infection in this world before antibiotics. It also may have helped. Houdini did show some improvement by Thursday and his temperature dropped below 100 for the first time. But he relapsed the following day and a second operation was performed for paralysis of the bowels. That operation was not successful and, as we know, Houdini died on Halloween.
I know this isn't as sexy as murder. But I'm willing to let the facts get in the way of a good story.