The Medford Public Library is co-sponsoring a virtual program with authors Katherine Ramsland and Tracy Ullman to discuss their most recent book, “The Serial Killer’s Apprentice,” a psychological examination of the blurred line between victim and accomplice — and how a killer can be created. If you are a fan of true crime and want to dive deep into the psychology of a serial killer and his apprentice, this program is for you. Register through the library’s online calendar to obtain the Zoom link.