According to Culture Trip, the dissection of bodies was illegal in the 1700s. Hewson, however, was eager to experiment, and so he turned to grave robbing to supply himself with cadavers (via Mental Floss). Hewson and others would either dig up the bodies themselves, or pay resurrectionists — professional grave robbers or body snatchers — a not uncommon practice at the time.

Historians later discovered that the bones found in the basement had cuts that matched those made by medical instruments, further supporting this theory. Moreover, the home was located mere blocks away from a wharf. Thus, bodies could be smuggled off ships or delivered to the wharf in the dead of night without arousing suspicion. At the other end of the street was a gallows, for executing criminals. Instead of risking getting caught and getting charged by disposing the remains, Hewson buried them in the house.

It’s unclear how involved Franklin was in this operation. According to Smithsonian Magazine, he was probably aware of what was happening, but did not participate. Of course, there’s also the possibility that Franklin, the face on the $100 bill, knew nothing. Whatever the case, Hewson was only 35 when he unfortunately died of an infection resulting from cutting himself while dissecting a body (via Medical History Tour).