The Computer Code Mystery, Paperback

Celia (11) and Anna (7) are inquisitive sisters who solve problems - usually with a new invention. When a mid-winter blizzard forces their school to shut down, they figure out how to amp up the family computer. Their favorite game becomes a supercharged adventure unleashing a chain of events involving the FBI, hidden computer code, a vile villain in a clifftop hideout, and three captive dolphins with a score to settle. Can the sisters crack the code in time to prevent the cyber-crime of the decade?