A Murder Is Announced — Agatha Christie

The date was advertised in the Gazette:

A MURDER IS ANNOUNCED
and will take place on Friday, October 29th, at Little Paddocks, at 6 :30 P.m. Friends please accept this, the only intimation.

Everyone thought it was a harmless game. And so on the night of October 29, the neighbors dropped by, just out of curiosity.

Then, as the clock chimed 6:30, the room went dark.

A gun exploded!

A body fell!

A woman screamed!

When the lights went on, a man was found lying on the floor. He was wrapped in a black cloak. He wore a black mask and he lay in a pool of blood--dead.

There had been thirteen people in the room--thirteen witnesses who might have identified the killer.

Who was the corpse? Who was the killer?

And why had this murder been announced?