Foundation and Empire is a novel written by Isaac Asimov in 1952. It is the second book in the Foundation Series. It takes place in two halves, originally published as separate novellas.

Warning: Wikipedia contains spoilers.

Table of contents
1 The General
2 The Mule
3 The Sequels

The General

The first half of the book, titled The General, is all about how the empire, now well into its collapse, launches an attack against the Foundation. They are led by General Bel Riose. The Empire, despite its decay, far outclasses the Foundation. Lathan Devers, a Foundation agent, goes on a mission to Trantor to attempt to see the Emperor. He fails and is nearly killed. However, the Empereor does recall and execute Riose, for being too sucessful and therefore too much of a threat. The war ends with the General's death.

The Mule

The second half of the book, titled The Mule, is all about the rise of a myserious man called the Mule. He is a man who has the ability to sense and manipulate the emotions of others. He uses this ability take over one of the sovereignties bordering the Foundation, and has them wage a war against the Foundation.

While his sovereignty is waging the war, he then travels under the guise as refugee clown with Toran and Bayta Darrell to different worlds of the Foundation, using his abilities to undermine the Foundations' war effort by destroying morale. In the end, the Foundation falls without much of a fight.

While still under the guise of refugee clown, he travels with Bayta and Toran, along with psychologist Ebling Mis to Great Library of Trantor. They seek to contact the Second Foundation to help get rid of the Mule. The Mule, on the other hand, wishes to know the location of the Second foundation so he can use the First foundation to destroy it.

The Mule surreptitiously stimulates Ebling's mind, allowing him to make powerful insights while using the library as a resource. As Ebling lies dying, the insights having come at the cost of his health, he is just as he is about to reveal the location of the Second foundation when Bayta shoots him. She had shortly before realized the Mule had been traveling with them. She kills Ebling to prevent him from revealing the location. The Mule, defeated, leaves them to go reign over the Foundation.

The Sequels

This novel is very closely tied into Second Foundation, which tells the rest of the Mule's story.

We learn in Foundation's Edge that the Mule was a rogue member of the planet/society Gaia.