The Subterranean Protocol

The 4:14 Express didn't just crash. It punched a hole into a history no one knew existed.
For disgraced engineer Sam Calder, the shrieking metal is a ghost from his past. But the true nightmare begins after the wreck.
He and a handful of survivors have fallen into a prison built by America's Founding Fathers, a place with its own merciless keepers and creatures that hunt by sound.
Hunted in absolute darkness, Sam must use the very skills that broke his career to deconstruct ancient traps and solve the prison's deadly logic.
Because in the tunnels beneath Philadelphia, the city isn't just a lie. It's the lock on a cage. And they just woke up what's inside.