CTU tries to find a mole in its midst, and a suspect hiding among the hostages at the airport introduces a harrowing new element to the terrorist equation.
A malevolent ghost in a wedding dress haunts Melinda's bride-to-be friend Lisa, and the spirit is reluctant to move on. Melinda learns the woman died on the day she married the man who's now Lisa's fiancÃ©, and she's determined to break up the couple.
After a warning about stress, Ed is a victim of identity theft; Sam's brother takes advantage of her hospitality; and Mike borrows Ed's car to impress a woman.
A DNA synthesizer that has the capability of customizing diseases is stolen from the campus where Charlie teaches. Don fears the thieves may be terrorists out to start or advance a bio-warfare program. He also believes the theft was an inside job and the chief suspect is one of Larry's top students. Back at home, Charlie discovers that his late mother was once a gifted musician.