The first part of the story is from the pov of Robert Mortimer, bank clerk, as he discovers a body on a church steps. In his shock he is befriended by John Gilliam, a gambler. But once his fortune has gone Gilliam is discovered dead, an apparant suicide. But Gilliam's cousin is not convinced and asks Dr Thorndyke to investigate.
An entertaining historical mystery ( )

Very good mystery. But it took me a minute to figure out that carbonic acid snow meant dry ice! ( )

This ingenious plot is divided into two separate sections. In the first of these Robert Mortimer,a bank employee,discovers the body of a man,slumped in a church porch. This man is later found to be dead and a constable is soon found to take control. Shortly after,a client of Mortimer's bank chances by and takes him for a restoring drink. The men become friendly and over a period of time Mortimer and the other chap,whose name is Gillam spend quite a time together. On one occasion Gillam takes the other to a 'gambling club. It transpires that Gillam is not only a serious gambler who loses more often than he wins,but is also being blackmailed. It therefore comes as no surprise when he commits suicide (or felo de se).
In the second section of the book,Mortimer consults Dr.Thorndyke,who at first is reluctant to take the case,which seems to him to be simple and obvious. he soon becomes interested however and together with his assistant (they always have an assistant) begins to investigate.
Apart from my usual quibble with Austin Freeman,that the explanation of how the crime was committed and the murderer brought to justice takes too many pages to explain,this is otherwise a fine crime story of its era. ( )