Recently retired from his duties in Hell, Lucifer Morningstar is managing his corporeal jazz bar when the angel Amenadiel arrives to give the devil an offer. A new unearthly being is granting humans their wishes, and fearing that the world will tear itself apart with this new power, Heaven has hired Lucifer as a third party to track down the wish granter's origins and put an end to its meddling in the affairs of men.