Former Ambassador Wilson reported back to the White House that there was no attempted purchase of "yellow cake" uranium from Niger, and said so publicly after the State of the Union message where Bush stated that Saddam was trying to buy nuclear components in Africa.
Someone in the White House then "outed" Wilson's wife as being a CIA agent. Often a death sentence for both the agent and their network of spies/informants/etc.
Nah, it wasn't anything so sinister. She wasn't an "agent," and wasn't endangered. Wilson himself spilled the beans, too. He's a slimy eel.