Zombies Don't Surrender

As the final volume in the series opens, Maddy, Dane, and Stamp are still together, though barely, nestled safely inside the walls of Sentinel City, a stronghold designed to keep Zerkers out—and zombies in.
Maddy trains night and day, hoping to join Vera as a Keeper. Dane has been given Sentinel Support in the form a busty blonde named Courtney. And what of Stamp? Although Maddy's dad has worked hard to rehabilitate him after his Zerker bite, he's still not all . . . there.
When Dr. Swift inadvertently allows the zombies' archenemy, Val, to escape from Sentinel City, Maddy's world turns upside down. She and Stamp are vanished—expelled from the safety of Sentinel City, no better than common Zerkers. Dane, a Sentinel now, escapes punishment and is assigned to ensure that his old friends never return.
As Maddy and Stamp stray from the safety of Sentinel City, danger mounts . . . and not just for them. Val has taken up residence in a seaside town and enrolled in another Normal high school. To outwit her and save Seagull Shores from all-out zombie Armageddon, Maddy must face her archenemy once again.
Only this time, she's all alone...