Contains spoilers for this episode and earlier episodes.
A body left outside National Health Services brings Jack Bauer back into a case he thought had ended with Ramon Salazar's arrest. Jack and his partner Chase Edmunds visit the prisoner as prosecutors prepare a cooperation agreement. Instead of signing, Ramon stabs his lawyer with a pen and blames Jack for what will happen next. Jack questions why Ramon chose this particular day to destroy the deal, then learns that the abandoned body carries a dangerous virus.
At CTU, Tony Almeida and Michelle Dessler begin tracing the victim while health officials explain the threat posed by the altered strain. An anonymous caller demands Ramon's release within six hours and threatens an outbreak if the government refuses. Jack suspects Ramon's brother Hector. In Mexico, Hector receives reports from Gael, who is watching the operation. Kyle Singer, meanwhile, has brought a bag of supposed cocaine across the border to earn money for his struggling family.
President David Palmer returns to Los Angeles for a campaign debate, accompanied by his brother Wayne and physician Anne Packard. Jack faces a more private crisis at CTU: his hands shake and he struggles to keep working without heroin. Kim now works there too and is secretly dating Chase. When her voice interrupts Jack as he prepares an injection, he stops, then throws the syringe across his office.