Ragnarok is the fourth full-length novel in the Jack Sigler/Chess Team series, following Pulse, Instinct and Threshold, as well as the prequel novel Prime, and eight standalone novellas focusing on the individual characters in the series.

It starts with a thunderous crack and a flash of light. Screams come next. Then the hunters. With a staccato flicker, the light disappears and everything within a hundred yard radius goes with it. A massive crater is all that remains where a chunk of the world has gone missing.

As the deadly phenomenon repeats and expands amidst the world's most densely populated cities--carving apartment buildings in half, scooping away entire city blocks, and claiming thousands of lives--Jack Sigler, Callsign: King and his black ops team take action. But the team is broken, spread across the globe and vulnerable. Scrambling to make sense of the violent disappearances and fighting to reunite, the team comes face-to-face with an otherworldly enemy capable of making the fearless...terrified.

Taking the battle to the ends of the Earth--and beyond--the team combats a savage enemy whose centuries-old plan for mankind has nearly reached fruition. If they fail, the planet will become little more than a fully stocked food cache for a creature whose presence heralds the beginning of Ragnarök--and the extinction of the human race.