In the novel Peril at End House, Jim Lazarus is an art dealer, working for the company Aaron Lazarus & Son on Bond Street. He is in love with Freddie Rice, and is also a friend of Nick Buckley and George Challenger.
He is described as "a tall, fair, rather exquisite young man, with a rather fleshy nose and over-emphasized good looks". He is interested in cars, and drives a long red car, with a "long gleaming bonnet of polished metal".
Lazarus once made an offer of fifty pounds on a painting of Nick's grandfather, Old Nick, which hung in the drawing-room at End House, but Nick refused to sell it. Poirot later found out that the painting was only worth twenty pounds, and asked Lazarus why he had made an offer greater than the worth of the painting. Lazarus explained that he knew that if he offered Nick fifty pounds, she would suspect that the painting was worth more, and get it valued elsewhere. Then, she would find that he had offered her far more than the painting was worth. After that, the next time he made an offer on a painting, she would be likely to accept without getting the painting valued elsewhere. He did this because there was a another painting in the room which was worth at least five thousand pounds.