Catch a Falling Knife. Lillian Morgan, #2

In the second book of the Lillian Morgan series (Thirteen Diamonds was the first) Lillian, a retired math professor, is jolted out of her serene life in a North Carolina retirement community when Mark, her granddaughter's boyfriend, is accused of sexual harassment. Since he has just started teaching at a small college the charge could end his career almost before it begins. Lillian finds that the school has a harassment policy from hell, but almost immediately a murder occurs and Mark becomes the chief suspect.
Ignoring her fingers-crossed promise to her son not to do any more detective work, Lillian springs into action and finds that in fact there are several other possible suspects. They include a student who doesn't believe in sex before marriage and a man who maintains a website that lists the license plate numbers of the cars belonging to patrons of local strip clubs. A key question concerns the identity of the mysterious Shooting Star, a masked dancer at Club Cavalier, one of the strip clubs under surveillance.
Lillian has to befriend the owner of the club and do other things senior citizens aren't supposed to before she can unmask the murderer.