Felina the cat queen may be gone, but the subway tunnels of Atlantia are still dangerous to all rodents who dwell within the twists and turns. Pup and his spider companion Hacklemesh are lurking in the shadows...

Hopper is determined to reach out to his brother-gone-bad, to see if he can talk some sense into the young rodent. But then Hope, the youngest of Zucker and Firren's new litter, goes missing, and all signs point to Pup as culprit.

Meanwhile, Firren is rattled not only by the disappearance of her daughter, but a shameful secret from her past that she's kept hidden for years. A secret that may hold damaging consequences for not only Firren, but all of Atlantia.

How can Pup betray his brother like this? What exactly is Firren hiding?

And will the tunnels ever be the same again?