Spoilers for this episode.
Michelle tells the hotel guests that an infectious substance has been released and that nobody can leave. Alvers supplies a description of his employer, but the first photographs CTU sends produce no match. Jack asks the staff to include people officially recorded as dead. Alvers then identifies Stephen Saunders, a British operative Jack believed had died during their mission against Victor Drazen.
Jack and Chase seek help from MI6 and collect Diana White, a woman connected to Saunders. While Palmer receives an untraceable telephone, Saunders demands that he use a particular phrase during a televised press conference. Palmer complies while the authorities watch for a possible signal. At the MI6 office, gunmen attack from a helicopter, killing Diana and wounding the officer helping Jack. Jack retrieves a hard drive before a bomb destroys the computer room.
At the hotel, Gael's condition deteriorates. Michelle visits him in isolation and offers a means of ending his suffering, which he refuses. After he dies, she asks Tony to obtain suicide capsules for guests facing the same illness. Chappelle allows Tony to take them despite the regulations. Saunders learns that Chappelle has been investigating his bank accounts. He calls Palmer with a new demand: Chappelle must be killed and his body delivered to a train yard by seven, or Saunders will release more virus.