On Thin Ice tells ice hockey player Marko Jantunen's fictitious tale of survival. The film begins in 2015 in the city of Lahti at the point where homeless Marko "Jarna" Jantunen has just hit the rock bottom. Debt collectors come to get their drug money, and Jarna is given 24 hours to pay his debt. This starts a drug-fuelled race against the clock. A manic pace, fear of the lurking killers, paranoia, and self-hatred about old injustices eventually lead to a traffic accident. Jarna has no strength left to run. The pace slows down and he is on the verge of giving up.