Enter a murderer is Dame Ngaio Marsh's second Inspector Alleyn novel, her first A man lay dead was a fun, but not particularly exacting or novel read, and gave little indication of what a good crime writer Marsh could potentially be. Enter a murderer shows her at the top of her game.
Set in the world of theatre, a milieu that Marsh loved (she was later awarded her "Damery" for writing and theatre production), this is a clever murder mystery. When Inspector Alleyn is invited to spend a night at the theatre by his friend, Nigel Bathgate (who also featured in A man lay dead), he looks forward to a night of fictional crime, but when an odious cast member is murdered for real on stage Alleyn is forced to investigate.
This is a very clever story with red herrings aplenty, and a great denouement. It's the sort of story where you have a suspicion from the beginning who the murderer is, but it's all very well disguised and keeps you guessing to the end. If you're into golden age detective fiction, you'll love this one.