Mrs Wilberforce is a sweet little old lady, rather eccentric with strict Victorian morals and nothing much to occupy her time. She has become rather fanciful and suspicious about neighbourhood activities. She often calls the kindly local bobby, Constable MacDonald, round for a chat about her worries but he has learned to take everything she says with a pinch of salt. 

Mrs Wilberforce lives with her sick parrot; General Gordon, in a gradually subsiding and lopsided house built over the entrance to a railway tunnel in Kings Cross, London. Although the house rattles and shakes every time a steam train whistles by, a certain Professor Marcus is more than happy to rent a room.

Unfortunately for Mrs Wilberforce, Profession Marcus is only superficially charming and is not the musician he claims to be. He is the brains of a small gang of criminals, all posing as amateur musicians, hoping to carry out a daring heist at Kings Cross Station.

Major Courtney is a nervous time, seemingly more upper-class than the rest, with a fascination for ladies' dresses. Harry Robinson is the youngest gang member, a pill-popping Jack-the-lad, obsessed with cleaning. One Round is a permanently punch-drunk ex boxer, never quite sure of what's going on or who is supposed to be. Louis Harvey is a psychotic Rumanian, carries a knife and is the most violent member. Not someone you would like to meet on a dark night! 

Of course, things go wrong when they unwittingly involve old Mrs Wilberforce. When she begins to see what they are up to, the only way to keep the old dear quiet is to bump her off. One by one they try but...…