At closing time the Barkley kids (Tim, 12; Sheila, 8; Billy, 5) are accidentally locked in the Harding Commerce Center, a large urban shopping center and office complex with state of the art security and interior environment systems controlled by a voiced computer called D.O.C. Deliberately hiding in there also while the place locks down around them are Midas, Mojo, and Sherman who intend to rob the Center's bank. Reassured by D.O.C., the kids don't panic but since the robbers disconnected the phone lines they can't call for help. D.O.C. did get out one report about a problem and Jim Harlan, the Center's head of security, hurries back to find out what is happening as the robbers work at opening the bank door and then the bank vault door. The kids help D.O.C. by spying and telling him what is happening when the robbers "blind" the security cameras that would show them at the bank door. When Mr. Harlan arrives and sees the situation he takes over the controls to keep the robbers from finding and capturing the kids. When the men do spot the kids, they chase them through various areas of the Harding's Department store both to keep them from sounding an alarm and to use as hostages if it comes to that.. Frustrated and furious Midas finally grabs young Billy to shoot him and the high-tech security systems must prevent that.