A murder is announced in the newspaper Gazette in the dizzy town of Chipping Cleghorn. Someone must be putting an invitation for a game in the paper. Naturally, a murderer would not place an ad in the paper announcing their murder, right? However dangerous as it might be, it sparks the interest of the people in town. With a specific date and time announced in the paper, the neighbors arrive at the home of Miss Blacklock ("Little Paddocks"). At 6:30, the lights cut out. After gunshots ring, the people at Little Paddocks quickly realize that announcement was NOT a game. When the lights come on, Miss Blacklock has an ear grazed by a bullet, and an unknown man lays breathless on the floor with a gun next to him.

A full on investigation takes place. The detectives must consider everybody a possible suspect. Who is the man dead on the floor? Did anyone know him? Was he trying to shoot at anyone in particular? Did he die from a suicide or an accident? Did anyone have anything worth killing for? Is everybody what they seem?

We meet the citizens of Chipping Cleghorn as they receive their paper on the morning of Friday, October 29th. There's old Mrs. Swettenham and her son Edmund. Edmund writes and is the intellectual type. Colonel and Mrs. Easterbrook are an elderly couple. Mr. Easterbrook is a former military man. Mrs. Easterbrook is a sweet yet simple-minded woman. Next, we travel to the home of Miss Murgatroyd and Miss Hinchcliffe. They are two elderly widows providing each other support and company in their old age. Finally, we arrive at the home of Pastor and Mrs. Harmon.

While reading the paper, they all notice something quite remarkable: a murder announcement! The Gazette's personal ad reads: "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." The residents of Chipping Cleghorn generally dismiss the announcement as the invitation to a game. It could be an exciting evening full of pretend murder and fun. Nevertheless, they should go see what the announcement's about, right?

Household by household, everyone we previously met arrives at Little Paddocks before 6:30. The people residing at Little Paddock are Miss Blacklock, her old school friend Miss Dora Bunner, and her second cousin's children Julia and Patrick Simmons. The maid, Mitzi, is the paranoid refugee from the war and Phillipa is another worker. The guests all pretend to drop by for frivolous reasons and not the announcement in the paper. Mrs. Harmon is the only one to bluntly ask if the murder had occurred yet.

Everyone still considers the whole situation a joke, so when the lights cut out, nobody expects what happens next. The gunshots kill the idea of a joke or a game. The lights come back on to expose a dead body on the floor with a gun next to his body. Also, a bullet apparently grazed old Miss Blacklock's bleeding ear. Bunny recognizes the dead man as someone who previously asked for money to get back to Switzerland. This seems to be the only contact the man had had with anyone else in the group.

The case is brought to Detective Craddock. He interviews the scene and the people who were present at the time of the crime. A letter comes to Craddock from a small, old woman: Miss Marple.

Craddock realizes that Miss Blacklock must have something that the culprit, whoever it was, wanted. After more probing, Miss Blacklock explains that she will inherit a very large sum of money when her old boss's wife dies. He made Miss Blacklock the beneficiary with no one closer to name. In a pinch, he named his estranged sister's children as the next in line.

Craddock, with the help of Miss Marple, starts investigating everyone involved. The more they discover, the more dangerous the situation seems to get. With the death count growing and time running out, the truth must be discovered.