Vedette Lim

George O'Malley's mother comes to Seattle Grace for help after another hospital botches her surgery; a medical miracle inspires the residents; Jackson's suspicions about Mark and Lexie interfere with work.

The team must infiltrate a drug trafficking gang after the robbery of a chemical plant leaves two customs agents dead; Nestor offers his help on the case, giving Maggie new insight into his character.

A call to the field may throw a wrench in Dawson's plan to retake the firefighter exam; the firehouse welcomes a new addition; Boden makes a bold move.

A fire at a boarding school shakes up Lt. Severide; Lt. Casey tries to help Dawson; Mills looks into his father's past.

The shooting of a child in their neighborhood forces Cruz and his brother to think about the gang; Isabella gets Mills to dress up for a gala; Casey feels sad he will be seeing Dawson less; Shay gets in deeper with Devon.

After a bomb leaves three people dead, the team presses a reluctant informant to gather information from his close friends who are under suspicion; OA and his girlfriend clash over where the informant's rights lie.