Fourteen-year-old Andrea once again travels back in time to uncover the secrets of an unsuspecting theft ring in the mysterious tunnels of Moose Jaw this time with her brother in tow.

Andrea would like to forget all about her trip back in time to the Prohibition days of the 1920s in Moose Jaw in Tunnels of Time. But then she agrees to take her younger brother Tony to their grandparents in Moose Jaw.

Andrea and Tony arrive only to find that their grandparents are missing! Then Tony learns about his sister's previous tunnel adventure, and decides to have one of his own. But he leaves his medication behind, and Andrea has no choice but to pursue him into the tunnels of the past.

Upon her return to the olden days, Andrea finds that her assistance is needed to expose a local theft ring and a corrupt police force. Will Andrea get Tony his medicine on time? Can Tony and Andrea learn to conquer their fears of growing up and being responsible? Can they expose the real crooks before they become trapped in the past?