One, two, buckle my shoe

A dentist lies murdered at his Harley Street practice... The dentist was found with a blackened hole below his right temple.

A pistol lay on the floor near his outflung right hand.

Later, one of his patients was found dead from a lethal dose of local anaesthetic.

A clear case of murder and suicide. But why would a dentist commit a crime in the middle of a busy day of appointments? A shoe buckle holds the key to the mystery.

Now - in the words of the rhyme - can Poirot pick up the sticks and lay them straight?