The Mystery of Ruby Queens — Betsy Allen

In the darkness beyond, Connie thought she could detect movements, imagined she could hear running footsteps, but she couldn't be sure. With every muscle taut, she listened intently. Yes, she did hear something, heavy breathing, just below her. But it seemed to come, suddenly rough hands gripped her ankles and her feet were torn from their teetering perch. Her hands felt for a hold she couldn't find, a crevice to cling to, a momentary block against the impending disaster that made her throat constrict and her heart pump wildly. In one last moment of consciousness she thought frantically, "I may be killed!"

When Connie Blair is sent on a research assignment to an old mansion in the heart of historical Philadelphia, she is catapulted into one of the most baffling mysteries she has ever encountered.