Mankind is no longer at the top of the food chain.

The Sixth Extinction is an apocalyptic tale about a pandemic that sweeps the globe, decimating the human race, leaving humanity struggling to survive. Within three weeks, everything has changed. Social structure has collapsed as the government locks itself away with a select portion of its vast army in deep bunkers, leaving the civilians to their own fate and the infected that stalk the streets.

Alex, Troy, Frank, Naomi, and the two King brothers find themselves taken to a secure island by their new friends aboard an old fishing boat led by a woman called Smokie. There is only a thin bridge that connects them to the mainland as they perch on the vast tidal lake.

Infected pack the bridge, kept at bay by a chain-link fence.

Tierra is sedated and moved to the medical hut after it becomes apparent that she suffocated her son due to her deteriorating mental state.

They believe they are safe until a scream, and animalistic calls wake them in the early hours. The vast lake has drained during the night. How? There is no time to find out as hundreds of creatures pour across the mud flats, flooding the island. The group has to fight its way across the bridge and then two miles down the road to get to the cargo ship before they are overrun. Do they have the strength after fighting and running for days with little sleep?

Meanwhile, Doctor Bachman and Emma are trapped inside a submarine on the surface of the reservoir, deep down, inside the bunker. The tentacled creatures are attempting to roll the vessel, trying to find a way in. Have they locked themselves inside their own tomb?