Sara questions her future as a CSI when a past case comes back to haunt her, the 12 year old Hannah, who has to back up her brother one more time with all new tricks up her sleeves.
There has been a bus crash and the patients are in the ER. Meredith and Derek's relationship gets more complicated when he dates a fellow doctor. Meredith's dad goes to visit her at the hospital.
In the season finale, Charlie accidentally puts Paddy's up as a prize for a dance marathon, which prompts the gang to enter the competition in order to save their bar.
The brothers capture a female vampire named Lucy who has no idea how she became one, which leads them to Dixon, a male vampire who is a little too giving. Gordon returns with a vengeance leaving Sam in danger.