The Frisby Waterless Murders — Julian Worker

The wrong person dies on a murder/mystery excursion.

Inspector Colin Knowles and Sergeant Rod Barnes investigate who murdered Major Ronald Harkness on a steam train in full view of 24 other people, none of whom seemed to notice.

When the forensics team discover three different people attempted to kill Harkness things become complicated for Knowles and Barnes. They have to go full steam ahead and see through the smokescreens placed in their tracks by the people who believe they're the murderer. 

Two people are going to be disappointed to find out they didn't kill the Major, but how do Knowles and Barnes find out who they are? By diligent police work, some skill, some luck, and a helping paw from their talismanic doggy friend Bingo. 

As Knowles and Barnes investigate, they find Harkness had many enemies and few friends from his time in the military in different parts of the world. The police are in a race against time before the murderer, and the two attempted murderers, strike again.
This is another exciting escapade for Knowles and Barnes and is the third book in their sequence of five.