When Gertrude Montague is orphaned, she is banished from her home by her rich uncle. She also hears that she will have a new nanny and tutor. Rather than the expected ex-nun this turns out to be a twenty-something, chain-smoking, posh British girl named Edwina Foxglove-Smitten. Gertrude happily gets into Edwina's convertible, unbothered by her fabricated resume and questionable past.

They are going to live at Mule Hall for the next year, a neglected Long Island mansion belonging to Gertrude's grandfather who is currently in prison for fraud. When they arrive, Gertrude is enchanted by the beauty of the house and the hundreds of magnificent paintings in gilded frames. Then, on her 14th birthday, she discovers she has the power to see the painted portraits of the house as living and breathing spirits who move through the house just like real people.

Gertrude realizes that she can use her powers to travel through the magical world of paintings and will have many adventures within them. She will also face great danger as she tries to help the characters within these paintings. She realizes that she may never gain love or admiration from her family, but she can gain self-respect and confidence through her rare ability to truly listen and empathize with all sorts of souls. But can she save these souls from the dangers they face?