It takes place primarily in Los Angeles but also in northern Mexico when Jack Bauer meets a family of drug dealers.

Throughout the day, Jack Bauer and President David Palmer attempt to stop the release of a deadly virus by Stephen Saunders – a former government agent.

Like the previous two seasons, there are two main acts in the plot: Day 3 sees CTU deal with a deadly virus threat that would be released in Los Angeles.

Back at CTU, it turns out that Tony Almeida, Gael Ortega and Jack have been working undercover on a sting operation.

When Michelle Dessler captures Alvers, he reveals that the mastermind of the day's events is a man from Jack's past named Stephen Saunders.

Gael is killed soon after being exposed to the virus and Michelle has to deal with the threat at the hotel, as well as the unruly guests who soon discover the deadly truth.

Saunders contacts President Palmer and gives him a series of assignments, one of which is the murder of Regional Division Director Ryan Chappelle.

It touches on many of the early plot points including the threat to release the virus, Jack's heroin addiction and the relationship between Kim Bauer and Chase Edmunds.

The website's critical consensus reads, "24's third day marks the series' most ruthless season yet with a breathless race to avert chemical catastrophe, a myriad of shocking surprises, and an unnerving disregard for treating any character as safe.