Following her stint in rehab, where she was diagnosed as having bipolar disorder, Zosia’s back at work and is taking her prescribed Lithium. But she’s thrown when Lisa, her mentally ill friend from the clinic, turns up. Not wanting to be reminded of her time there, Zosia orders Lisa to leave.

Lisa finds a way to stay at the hospital, however, and ends up being treated by Jesse. When Lisa realises he’s the Jesse who dumped Zosia, she discharges herself. But Jesse’s worried and tells Zosia that her friend uses cocaine to counteract the numbness caused by her medication.

Concerned, Zosia tracks down Lisa, who’s taken an overdose, and has her friend rushed back to Holby where she’s saved. As she talks to an unconscious Lisa in intensive care, Zosia vows not to become like her. Will Zosia carry on taking the Lithium?

Also, Serena battles against the belt-tightening recommendations of the Holby board when chairman Angus Farrell comes down to AAU and starts advocating some fierce cuts. Can Serena show him she has everything under control?