Ravenhill Correctional Institute, a notorious, maximum-security prison in Miami, Florida, home to the abandoned military prison, the Glasshouse. Hurricane Anna–a superstorm made up of two Category 5 hurricanes coming together to wreak unprecedented havoc along the eastern seaboard.

When the superstorm hits, the corrections officers at Ravenhill flee, opening all the cell doors and leaving the inmates to fend for themselves as the floodwaters rise. But Jack Constantine–an ex-cop serving ten years for killing one of his wife’s murderers–isn’t going to just lay down and die. Not when his wife’s two remaining killers are among the prisoners relocated to the Glasshouse to ride out the storm.

Meanwhile, Kiera Sawyer, a corrections officer on her first day at work, is the only officer left behind when the others flee. Sawyer rescues Constantine and offers to team up. If they can make it to the Glasshouse, they might just survive the hurricane. But that involves making their way through the prison, fighting off eight hundred blood-crazed inmates as the building fills with water and the walls crumble all around them.