Welcome to the FBI (Federal Bureau of Ingestigation). This case is confidential. We hope you can stomach it. Facts: Southport Grocery & Cafe serves fresh comfort food for breakfast and lunch only (or so they say). Claim: We suspect a monthly Secret Supper. Leads: Menu is allegedly seasonal. Owner Lisa Santos appears to be testing recipes with chef Derrick Dejaynes. Evidence: Four courses. Prix fixe, wine included. Starter salad is grapefruit and avocado with a vanilla vinaigrette. Main course is lamb pot pie. Last-minute addition: monkfish with black licorice sauce (sounds fishy). Dessert will be a Bailey’s Irish mousse sandwich. First Supper Stakeout: Friday, 7 p.m. Southport Grocery & Cafe, 3552 North Southport Avenue, at Addison Street (773-665-0100 or southportgrocery.com). Space is limited. Call ahead to make a reservation or sign up for the newsletter for news about the next supper.