The newly assembled Librarians investigate a mysterious dancing sickness, leading them to a showdown with a powerful magical factioneer at a professional ballet company.
Charlie, Lysa and Connor find themselves in a strange manor with ongoing Christie-style murders. As they work to solve the mystery, Vikram searches for them with help from a tarot reader.
After a bachelorette party with Lysa's best friend from childhood, the team wakes up in rough shape and with horrible hangovers. They also have no idea how they ended up where they are.
When Vikram attempts to return to 1847 via a homemade time machine, he inadvertently transports the entire team back to the days of King Arthur, where they learn the truth about a Knight of the Round Table, Camelot, and Elaine.