Black Ice (2007)

Upon discovering that her husband is having an affair, a Helsinki gynecologist attempts to gather more knowledge about her rival and, in the process, becomes hopelessly entangled in the other woman's life - partially on purpose but primarily out of happenstance. Saara is pretty, elegant, liberal, and friendly to a fault. Yet while surface appearances would suggest that Saara is something of an open book, the truth is that lately no one has looked deeper enough to notice otherwise. Driven by jealousy to find out why her husband Leo has grown distant as of late, the sleuthing wife soon discovers that her spouse has recently entered into an affair with a young student and part-time martial arts instructor named Tulli. Her desire to learn more about Tulli growing with each passing hour, Saara eventually signs up as a student in one of the woman's self-defense classes. Eventually, Saara integrates herself into Tulli's life by blending fact and fiction to create a new persona. While Saara's crafty bid to find out more about Tulli without revealing her true identity is indeed successful, her deceptions start to snowball after she creates a fictitious lover in order to mislead her husband. The satisfaction of turning the tables on her husband gradually begins to dissipate, however, when the complex web of deceit becomes too unwieldy to maintain, plunging everyone involved into a hopeless cycle of despair and revenge.