Precious Dragon

The spell-casting detective and his demonic partner go to Hell on a fact-finding mission in this "pleasantly suspenseful . . . fantastical mystery" (Publishers Weekly).
For years, the embarrassing secret of the Singapore Three police department was Detective Inspector Chen-a specialist in the supernatural whose jurisdiction extended to Heaven and Hell. But when a rampaging goddess nearly destroyed the city, only to be stopped by Chen and his demonic partner, Zhu Irzh, the department was forced to reward them, resulting in the kind of attention that both cops loathe. Their new assignment is an affair of state, escorting the Heavenly functionary Mi Li Qi on a diplomatic mission to the underworld. By the time they're finished, Chen and Zhu Irzh will wish they had remained forgotten.
Soon after they check in to their hellish hotel, Miss Qi vanishes into the abyss. They follow her into the bowels of the demonic bureaucracy, where they will be forced to dodge all manner of otherworldly dangers if they wish to avoid a political incident with apocalyptic implications.
Precious Dragon is the third of the five Detective Inspector Chen Novels, which begin with Snake Agent and The Demon and the City.