How do you catch a thief who isn't there? Ruby discovers the perils of throwing caution to the wind as she embarks on her fourth adventure.

Ruby Redfort has a lot of reasons to feel confident. Undercover agent, code cracker, thirteen-year-old genius — she's one fearless kid, buster. Unmasking an evil villain? Done. Honing her parkour skills by climbing skyscrapers and leaping across roofs? All in a day's work. Heeding the warning signs? Well, not so much. When a ghostly foe begins stealing from the highest buildings in Twinford, Ruby Redfort is ready to defy death one more time to capture the bandit. But fearlessness can lead to taking risks, which can land a person in very serious trouble. While Ruby may think she's invincible, there's truth to the saying that recklessness always comes before a fall.