The next day is Sunday. The four members of the Secret Mystery Club meet in their treehouse in Billie’s backyard. Mika has brought a packet of Japanese biscuits for them to share because she knows they are Billie’s favourite.

Billie pulls one of the long chocolate-covered sticks out of the box and chomps on it like a rabbit while the others stare at the photograph of the boot print.

She and Jack give each other a look and Billie feels her tummy bubble with excitement. She can’t wait to hear what Mika and Alex have to say about the new clue they have discovered.

‘Hmm. That is definitely a man’s boot print,’ Alex says.

He is peering carefully through Billie’s magnifying glass. ‘And there are no men living at your place, are there, Mika?’

‘Nope!’ says Mika confidently. She takes the magnifying glass to look at the photograph herself. ‘Oh, wait. There’s Gus.’

‘Gus?’ they all ask together.

‘He prunes the trees. And cuts the grass.’ Mika shrugs. ‘He put the netting over the strawberries for Mum. That’s probably his boot print.’

‘What?’ says Billie, choking on her chocolate stick.

Jack looks upset, too. ‘Well, maybe he’s the thief, Mika? He could easily lift up the netting and peg it back down without anybody knowing. Couldn’t he?’

Billie and Alex nod in agreement.

‘He’s allergic to strawberries. He told me when he was putting the netting down,’ Mika says, shaking her head slowly.

‘Sorry guys. I guess we’re back to square one.’

Billie lets out a deep sigh. How disappointing! She takes another chocolate stick to make herself feel better.