"I wish I wasn't a twin." Twelve-year-old Jolene is determined to find independence from her brother, Michael, during a family trip to research the Halifax explosion of 1917 for her father's Museum of Disasters. When her grandfather finds a time crease into the past, Jolene discovers a new friend and the importance of family and loyalty in a world torn apart by World War I. When Michael joins them, however, the past suddenly becomes much more complicated.
Michael inadvertently threatens Jolene's friendship with a grieving family, and his careless comments spark speculation that they are spies. Together, the twins try to reconcile the honour and horrors of the Great War as they struggle with the knowledge that their new friends are living in the area soon to be devastated by the explosion. Jolene knows they can't change history, but Michael is determined to try and leads them into the midst of destruction.
In the harbour, the Mont Blanc, laden with explosives, collides with the Imo and bursts into flames. Minutes later, two thousand are dead, and nine thousand more are injured or trapped in shattered burning buildings. The day that changed Halifax forever also changes Jolene and her twin brother.