How Can I Be Sure?

Thea Doukas is on a downward spiral, attempting to recover from a broken heart after her lover Leonie Brandt marries Pia Hartmann. On the rebound, she goes from affair to affair, until she finds some peace staying with Suzanne Weigl and her wife Beth in their house on lake Starnberg.
A dilapidated house next door is up for sale and Leonie suggests they buy it together. Thea is doubtful she can ever live so close to Leonie and Pia, until she meets Leonie's best friend Emma Stoiber. Winter sport dominates the area, and Emma is on the German biathlon A Team. Thea is immediately infatuated, but Emma has a boyfriend. A full-blown crisis erupts when an intimate photo appears in a scandal newspaper. They separate, their expectations too difficult to reconcile.
A slow-burn romance between two women from very different worlds.
This is the fourth book in the Starnberg series.