Transcript of opening video narration track

That December morning is cool and clear - you know those sorts of mornings.

Halifax is buzzing with life - people heading out to factories and shops, kids walking to school.

It’s a pretty busy city. The first world war still rages, and Halifax is an important hub, and far from danger. At least, that’s what everyone thought.

Just moments after sunrise, out there in the shipping channel, the S.S. Mont Blanc is arriving.

The plan is for it to join a convoy of ships bound for France. On board are explosives meant for the allies.

At the same time, the S.S. Imo is preparing to make way to the harbour from a bay where it had anchored overnight. It too is on an urgent mission - carry grain to Belgium, the war there had left people literally starving to death.

Across the hull, right there, a big “Belgian Relief” sign. That’s supposed to act as a signal to the German submarines not to attack. But the Imo would never even make it to the open ocean.

Out of the blue, a steamship cuts across the Imo’s path. In a hurry, the pilots agree to pass each other on the right side, to avoid a collision. That probably seemed sensible, but they were breaking the rules of navigation, and the Imo is now in the path of oncoming traffic.

Remember that cargo ship the Mont Blanc? It is gingerly moving its way between two packed ferries in these busy waters. There’s no way the passengers could know the nearby ship is full of explosives.

You see, typically a ship like this would carry a flag warning of its dangerous cargo. But it’s wartime. A warning flag would only invite a torpedo attack, so there isn’t one.

The Imo, still in the wrong shipping lane, is suddenly facing a tugboat towing two long coal barges. The quick-thinking tug captain turns back toward Halifax, but it’s too late. The Imo is a bit trapped - it can’t correct its course. Which means the worst.

It is now right in the path of that explosives-laden Mont Blanc.

Did the captains see the danger right away? You see, by law this is the moment when both should reverse their engines, but they don’t. The Mont Blanc signals that it has the right of way and is staying the course. The Imo signals that it won’t yield. Likely very scared, the two captains cut their engines, but the momentum keeps the ships moving forward.

So imagine this. Mont Blanc can’t steer to the right. If it does it might run aground. The whole ship might explode.

Instead, the captain makes the only decision he has left - steer the Mont Blanc toward Halifax, right in front of the Imo.

And listen to this. That is the sound of Imo’s engines suddenly being thrown into reverse.

Too late, though. The ship ends up pivoting in place and rips into the side of the Mont Blanc.

The gash is three metres long. That opens up several barrels of flammable benzol that spill all over the deck and over the side.

Metal grinds against metal. That creates sparks, and the fires start right away, crawling along the deck of the explosives-heavy Mont Blanc.

The captain knows how bad this could be and orders his crew to abandon ship.

As they flee, rowing furiously towards the Dartmouth shore, those crew members are waving and shouting at nearby ships, just trying to warn everyone to get away.

No one seems to understand their warnings. Maybe it’s the wind and the distance and the panic. Maybe it’s because they’re yelling in French.

Pretty dramatic scene, a ship on fire. Crowds start to gather, to run to the port to look. Firefighters show up.

They have no idea what the Mont Blanc is carrying below deck.

One compartment holds gun cotton. Two others contain TNT. And stored throughout is something called picric acid. That’s an extremely dangerous chemical used in the manufacture of artillery shells. It’s even more powerful than TNT.

Basically, the Mont Blanc is a massive bomb waiting to explode.

9:04 a.m. - it happens.

In an instant all buildings within 800 metres are destroyed.

1600 people are killed right away.

9000 are injured.

The acrid smell of smoke and explosives chokes the city.

All these years later, the Halifax Explosion remains one of the worst disasters in Canadian history. All that loss from small moves, tiny decisions, on a clear December day.