In 1998, a group called the Friends of Benjamin Franklin House began renovations on Franklin's London residence, No. 36 Craven Street, and discovered a nasty surprise: 1,200 pieces of bone from 10 bodies, six of which were children. And the bodies were buried in the basement around the time Franklin was living in the house.
No, Franklin didn't engage in a murder spree in between penning Poor Richard's Almanack and flying kites in lightning storms. In fact, it's unlikely that the bodies were murder victims at all. The bones were sawed through and bore scalpel marks, suggesting the bodies were used for an anatomical study. And it just so happens that Franklin's dear friend William Hewson, whose mother-in-law owned Franklin's home, was a student of the famed anatomist William Hunter. Historical speculation holds that Hewson, after digging up these bodies or paying a "resurrection man" for the remains, set up a lab in Franklin's basement for his own anatomical studies.
The question remains, however: did Franklin know about the bodies? It's possible that he participated in, or at least witnessed Hewson's studies, but Hewson could have used the basement — and then buried the bodies — when Franklin wasn't around. Without further historical evidence, we can't know if the bodies in the basement would have been as much of a surprise to Franklin as they were to the renovation team.
That Time They Found Those Bodies in Ben Franklin's Basement [mental_floss]