After settling in Green Hills, Sonic is eager to prove he has what it takes to be a true hero. His test comes when Dr. Robotnik returns, this time with a new partner, Knuckles, in search for an emerald that has the power to destroy civilizations. Sonic teams up with his own sidekick, Tails, and together they embark on a globe-trotting journey to find the emerald before it falls into the wrong hands.

Bored and unhappy as the Lord of Hell, Lucifer Morningstar abandoned his throne and retired to Los Angeles, where he has teamed up with LAPD detective Chloe Decker to take down criminals. But the longer he's away from the underworld, the greater the threat that the worst of humanity could escape.