A New York Times bestseller! Perfect for fans of The Babysitters Club and anyone interested in computer science, this series is published in partnership with the organization Girls Who Code.

Loops, variables, input/output - Lucy can't wait to get started with the new coding club at school. Finally, an after school activity that she's really interested in. But Lucy's excitement turns to disappointment when she's put into a work group with girls she barely knows. All she wanted to do was make an app that she believes will help someone very special to her.

Suddenly, Lucy begins to get cryptic coding messages and needs some help translating them. She soon discovers that coding - and friendship - takes time, dedication, and some laughs!