On April 13th 1976, a devastating munitions factory accident shook the town of Lapua, Finland. Hundreds of kilograms of gunpowder ignited, causing an explosion that took the lives of 40 workers. Lapua 1976 tells a story of love, life, perseverance, grief and hope in the face of unbelievable calamity.

Middle-aged municipal architect Mikko is frustrated with his job and his marriage, so for years he has directed his energy into renovating a turn-of-the-century wooden villa on the seaside. One beautiful summer evening Mikko and his wife Liisa invite old friends to a party in the villa: divorced intellectual Erik who gets along a little too well with Liisa; and noisy building contractor Hessu with his young and sexy new wife Pirre. Their increasingly drunken discussions are interrupted by a surprise visit from Mikko's and Liisa's daughter Jonna and her husband Pete. A conflict between the father and the daughter ensues in front of the guests.

Hese, the shy owner of a video company, travels on a moped to film a commissioned Christmas party. From the steps of his office, Hese finds an anonymous Christmas present, a Hese slipover, and begins to find out who it is from.