Seokga the No-Longer-Fallen is working on himself. Reinstated as a god, the trickster now attends much-needed therapy, even as he desperately searches for his lost love, Hani. But when the red thread of fate tangled around his finger--signaling Hani's reincarnation--leads Seokga to a luxury cruise down the river of the dead, the woman he finds waiting for him isn't Hani . . . she's Yoo Kisa, and she has no memory of him.

Yoo Kisa is exhausted with her afterlife. While she'd hoped the underworld would be peaceful, whoever she was in a past life racked up quite the karmic debt, and now she must pay it, working thanklessly aboard the SRC Flatliner. Even worse, the red thread wrapped around her pinky followed her into the underworld . . . and although her fated partner has found her, he seems to find her lacking.

When the heavenly emperor is murdered aboard the ship, Seokga and Kisa must solve the crime before the cruise ends. As the mystery draws them closer, the god and the gwisin will have to decide what they truly mean to each other. But there's something bigger at play aboard the SRC Flatliner, something that holds the key to Kisa and Seokga's fated connection--and the fate of the mortal and heavenly realms.