Strange things have always happened in the Superstition Mountains of Arizona… Bizarre lights, reports of cave entrances that appear and then vanish, hundreds of mysterious disappearances…and rumors of monstrous creatures that inhabit a labyrinthine underworld.

When a terrifying accident on an Arizona highway leads to a military exclusion zone and a cover-up of staggering proportions, Jack Sigler—Callsign: King, field leader of the elite and ultra-secret covert Chess Team—joined by his closest friend, archaeologist George Pierce, sets out into the desert, intent on discovering the truth.

Assisted by a beautiful paranormal investigator, dogged by soldiers intent on preserving the quarantine, and pursued by a relentless legendary hitman, King soon finds himself in a race against time to prevent all out war with the creatures that inhabit the underworld.

Callsign: King – Underworld was the fourth in a series of Chess Team novellas released in 2011, and the sequel to the first Callsign: King story. Each of the eight books in the series—deemed the ‘Chesspocalypse’—follows a single member of the team and is co-authored by Jeremy Robinson and one of six other fantastic authors. The stories take place after the events of Threshold, the third Jack Sigler thriller, and before the events of Ragnarok, the fourth full-length novel in the series. The Chesspocalypse novellas are designed to introduce readers to the series. If you haven’t read the novels, no worries. Enjoy the ride!

Praise for Robinson

“Rocket-boosted action, brilliant speculation, and the recreation of a horror out of the mythologic past, all seamlessly blend into a rollercoaster ride of suspense and adventure.”
—James Rollins, New York Times bestselling author of The Eye of God

“With Threshold Jeremy Robinson goes pedal to the metal into very dark territory. Fast-paced, action-packed and wonderfully creepy! Highly recommended!”
—Jonathan Maberry, New York Times bestselling author of Rot & Ruin

“Jeremy Robinson is the next James Rollins”
—Chris Kuzneski, New York Times bestselling author of The Einstein Pursuit

“If you like thrillers original, unpredictable and chock-full of action, you are going to love Jeremy Robinson...”
—Stephen Coonts, New York Times bestselling author of Pirate Alley

“How do you find an original story idea in the crowded action-thriller genre? Two words: Jeremy Robinson.”
—Scott Sigler, New York Times bestselling author of Pandemic

“There’s nothing timid about Robinson as he drops his readers off the cliff without a parachute and somehow manages to catch us an inch or two from doom.”
—Jeff Long, New York Times bestselling author of The Descent


Praise for Ellis

“Some books are just plain unbridled fun, others are edge of the seat gripping entertainment, some make you think, a few open your eyes. Sean Ellis is a magician, doing it all with a deftness that pulls you in and draws you along from page one breathlessly to the end of the book.”
—Steven Savile, international bestselling author of Silver

“Sean Ellis delivers another high-octane romp, exploring mythical lost civilizations and alternative histories, with the unrelenting pace of your favorite summer blockbuster.”
—Stel Pavlou, bestselling author of Decipher

“[The Adventures of Dodge Dalton in the Shadow of Falcon’s Wings] is high flying adventure at its best. Cleverly conceived, original, and multi-layered, the action literally jumps off the page and takes the reader through unexpected twists and turns.”
—Rob MacGregor, New York Times bestselling author of Indiana Jones and the Last Crusade and Hawk Moon