Massachusetts State Police Agent Lili D'Amico and retired engineer Gil Novak were enjoying their first winter together in Florida. Responding to a commotion, Lili finds her neighbor Martha being attacked. After Lili intervenes, she accompanies frail Martha to New Hampshire, where they find that someone had been in her home.

While Lili continues her involvement in Martha's case, Gil is asked to consult on a separate case about recently dug tunnels that have mysteriously appeared in his hometown of Greenfield, Massachusetts. A retired robotics engineer, Gil is recruited to build and operate a robot to inspect the tunnels for clues to their origin.

In this thriller, Gil and Lili end up working together on both cases, as more people flee from unknown pursuers with obscure motives. This is Hy Shaw's second book in the Gil Novak and Lili D'Amico series.