Jack Harvey and Emma Morgan return in a high-stakes race against time.

In 1944, Nazi scientist Klaus Richter built a quantum cipher machine, decades ahead of its time, before vanishing along with the secrets of Operation PO Box 1142. Eighty years later, people are still killing to keep that device hidden.

When CIA agent Jensen Hunter’s sister, historian Dr. Marin Hart, disappears after uncovering references to “the Helix,” Jensen is ordered to stand down. Another agency has taken over. Progress is nonexistent. And Marin has only seventy-two hours before she becomes collateral damage in a conspiracy older than the Cold War.

The Spiral Group, a shadow network born in 1945, has taken her. They’ve murdered to protect the Helix before, and they’ll do it again. With his badge suspended, Jensen goes rogue. His partner Adeline Chase joins him, risking her career to save Marin. Jack and Emma, treasure hunters Jensen once helped, drop everything to repay the debt.

Four outsiders. No authorization. No backup. A trail of bodies leading into Europe’s darkest corners.

The Helix is real: a quantum cipher that has control over the economic layout for many countries and is controlled by the Spiral Group. The quantum cipher’s full potential is yet to be realized and awaits the proper entry code to release its full power, which will give it control over triggering global missile systems. Only the original cipher from 1944 can unlock the quantum cipher network. Marin is the key to finding it, and the bait in a trap meant to erase anyone who gets too close.

To save her, this makeshift team will have to become what they’ve never been: ghosts operating in the shadows, hunted by the Spiral Group’s assassins, suspended by their own government, racing against a clock that’s already counting down to zero.

Two partners willing to sacrifice everything, and two treasure hunters who are all in over their heads. Seventy-two hours until Marin dies. And a secret that powerful men have murdered to protect for eighty years.

But some secrets are more dangerous than the people who keep them. And some conspiracies never really end.