A plumbing leak becomes a flood, causing chaos at Seattle Grace; the chief tries to implement new teaching policies; George tries to take his residency exam again; Derek hopes to move Meredith's roommates out of her house.
Hetty and the team continue searching for an elusive book that has the attention of foreign security agencies.
Tony sees a former police informant he believed to be dead, when the team investigate the death of a sailor outside Baltimore.
When the remains of a storm chaser are found, it seems that they died while following a tornado. But the team soon uncover evidence to suggest that he was murdered.
Sandy is trying to patch things up with Kirsten.