The Mercer Monster Mash is back, as local businesses take to the streets of Princeton to celebrate Halloween. https://www.youtube.com/watch?v=y3ytontmpiU It's happening Oct. 31 from 6-10 p.m. in the Grassroots District of downtown Princeton. The event is being put on this year by the RiffRaff Arts Collective, with help from the city of Princeton and other