Six-year-old Eloise loves to take a bath, which is bad news for Mr. Salomone and the elegant people gathering below in the Plaza's Grand Ball Room for the charity event of the season, a Masked Ball.

Wealthy, popular Webber Academy senior, Caroline, permits her new friend and classmate Waverly, an autistic, gay, scholarship student, to attend the annual Masquerade Ball disguised as her; but the evening becomes a nightmare when there is a global blackout, and Waverly and her friends discover what the school's dean and top donors really have planned.

"The Thea Sisters are headed to Venice, Italy! They'll be there for the Carnival, an annual festival that's famouse for its elaborate masks. The mouselets love exploring the city's bridges and canals, and seeing the beautiful costumes mice wear to Carnival celebrations. But a mysterious thief strikes while they are there! Can they unmask him before the festival ends?"--Page 4 of cover.