Dead reckoning

Jett is a girl passing as a boy, living as a cowboy in the old West as she searches for her long-lost brother. When the book opens, she's just rolled into a new town, where she stops by the saloon. Things are relatively calm, although she suspects there will be Trouble from at least one of the locals. Sure enough, Trouble starts to mosey over, when—The saloon is invaded by zombies. Barely escaping with her life, Jett hightails it out of town and soon falls into the company of Honoria Gibbons, a smart, self-sufficient young woman who also happens to be a fabulous inventor. Together with White Fox, a young man they meet, they set out to discover what's caused the zombie uprising. Turns out these zombies aren't rising from the dead of their own accord... but who would want an undead army? And why?