Spiral

In the fifth and penultimate book in the Tunnels series,
The Styx have surfaced. If you thought the Limiters were nasty, think
again. They've brought their females with them this time. And
all that stands in their way are Will and his friends, and a rag-bag
team of retired commandos. It's a smoking spiral of chaos and
not everyone is going to survive. Highly-anticipated fifth book
in the internationally bestselling Tunnels series.