An explosion in the center of Lac-Mégantic will change the destiny of its inhabitants. Gabrielle gets a music recording contract. Patrice surprises him. One week before the event, Marco and Julie are preparing their wedding.

Two months after the event, the trauma is more and more present. The police must intervene with Corine. The day before the tragedy, the Lamarre brothers were worried about their sister Julie who was going through a breakup. Annick comes to Corine's aid.

Vincent tries to step back and calm his family's distress following the tragedy, even if he sometimes considers doing something drastic. Before the tragedy, it's a party for the Lamarres, except for Julie who is going through a difficult time.

Bryan, a volunteer firefighter, experiences the consequences of the tragedy and sinks into depression. He reconnected with Myriam, his childhood sweetheart. His relationship with his girlfriend is strained.

Annick is no longer able to live her life normally following the events. The evening of the tragedy, she joins an old flame and arrives late at the Musi-Café, narrowly avoiding death. Marco helps evacuate the city center.

Faced with this devastation, Father Rémi questions his own faith, along with Marco and many other residents. On the day of the tragedy, Marco and Marie prepare their wedding. The sewers fill with oil and Marco, in a heroic move, saves the day.