From the back cover:
There's a Fungus Among Us!
Worse yet, it's some of that alien Fungi from Yuggoth!
Time and space are bent all to Hell when members of some elder races from H. P. Lovecraft's Mythos stories suddenly turn up in the Weird West™. When the undead gunslinger Ronan Lynch and an Irish huckster named Reg get tangled up in this web of inter-dimensional intrigue, it's up to them alone to terminate the mi-go's mysterious experiments with ghost rock and boot their alien butts back home once and for all.
And if they should fail, the Reckoners are going to have some bad company!
This Dime Novel™ includes a full-length novella and an official Deadlands™:The Weird West™/Call of Cthulhu® adventure.