Alison Sweeney and Cameron Mathison are back with a new Hallmark mystery.The stars are reprising their characters from the popular Hallmark Movies & Mysteries movie franchise, ET can exclusively reveal, but with a twist: They'll be kicking off a new mystery!Sweeney will again play the fan-favorite Hannah Swensen in the upcoming film, and Mathison, who will wrap up as co-host of Hallmark Channel's in August, will return as Mike Kingston.