Doherty, riding on his motorcycle, is first to arrive at a multivehicle collision; Taylor is hit by a car; Tatiana goes to see Chevchenko, and tragedy ensues.

Bosco is dismayed as he watches Cruz go to the extreme lengths of planting drugs, frightening children, and faking a dying declaration in their attempt to arrest the drug dealer who killed another dealer and then tried to to kill the 12 year old boy who witnessed the crime; Nancy tells Ty that she's ending her relationship with Hancock, and gives Ty the ammunition he needs to get out from under Hancock's thumb and back to duty at the 55, as well as getting Sully's suspension from duty lifted.

Bosco and Faith chase after people who have stolen money from a crashed armored van. Kim meets a journalist. The girl who accused Carlos attempts suicide, and the truth comes out.

Yokas clashes with her mother over her recovery; Maritza is back on the job, but unhappy that she's back in the bag and handing out parking tickets; Ty and Sully discover a truck carrying sick illegal aliens and end up scouring the city to track down one of them who escapes after it's determined that the aliens have a highly contagious and potentially fatal disease.

Doc is demoted back to the streets and continues his downward spiral, presenting Kim with no end of problems as he lies about his demotion, resists her orders as the supervising paramedic, and deliberately runs down a perp with the bus; Barnes is shanked at Riker's for doing a flip on Buford; Carlos is devastated when Kylie is diagnosed with aplastic anemia and he's not a match for a bone marrow donation; Sully tries to deflect Ty's teasing about his relationship with Barbara by getting him to focus on their LSAT prep; after a horrific gunfight, Maritza finally captures Lettie's killer and decides to spare him so that he can suffer for the rest of his life in prison.