Angel and the actress

Award winning actress, Joan Minter, is murdered in front of a gathering of her closest friends. However, nobody knows who the murderer is, nobody saw him or her, and nobody present could possibly be the guilty one. That's the challenge facing Detective Inspector Angel and his team when they are called out to her luxurious home in Bromersley, South Yorkshire, at the foot of the Pennines. At the same time, an apparently innocent young insurance man is found murdered in his own house. The only clues are a new vacuum cleaner left by the murderer and an open refrigerator. Who committed the crime and what has the vacuum cleaner got to do with the case?