The Secret Mystery Club climb down from their treehouse, determined to find more clues.

Jack and Alex have decided they will talk to Mika’s neighbours, to ask if they saw or heard anything unusual on the night of the robbery.

Billie and Mika are going to visit Alf in his corner shop.

Alf is sure to know something, Billie thinks. Carrying rolled-up posters under their arms, she and Mika walk down the street. Alf knows everything about everyone.

Billie pushes open the glass door and the little bell rings. Alf comes out from the back of the shop, wiping his hands on his big grimy apron.

‘Hey, kids,’ he says in his gruff voice. ‘What can I do for you?’

Billie looks at Mika. But Mika has gone quiet and her cheeks are turning pink. Billie has forgotten that sometimes Mika gets nervous talking to people she doesn’t know very well.

Even though Billie knows Alf is kind, he doesn’t smile much, which can make him seem a little unfriendly. So she quickly steps in front of Mika.

‘Um, we’ve done some posters at school about saving the environment,’ Billie says. ‘We were wondering if we could put them up in your window?’

Alf points to the front of the shop. ‘If I take any more of your posters I won’t be able to see out my own window!’

Billie and Mika turn to look. They had been so busy chatting on the way in that they hadn’t paid attention to Alf’s front window.

It is already full of Saving The Environment posters. Billie recognises posters from lots of people in her class — and other classes, too.

‘Sorry, kids,’ he says. ‘You’ll have to find somewhere else to stick them. My window’s full.’

Billie sighs. This day is turning out to be full of disappointments!

‘That’s all right,’ she says glumly. ‘Thanks anyway, Alf.’

Billie turns to walk out of the shop. I hope Jack and Alex are having more luck than us! she thinks.

‘Wait!’ Mika’s voice comes out as a squeak. Billie turns around in surprise to look at Mika.

‘Yes?’ Alf says gruffly.

Mika’s cheeks turn pinker, but she takes a big breath and continues. ‘I was just, um, wondering, who made your jam?’

‘Hmpf?’ Alf says, looking puzzled.

‘The strawberry jam on the counter,’ Mika insists. ‘The sign says it’s home-made.’

Billie feels her tummy flutter with excitement. Go Mika! she thinks.

‘Oh! That’s Andrea,’ Alf says, picking up a little glass jar and turning it over in his big dry hands. ‘She said she made such a big batch she couldn’t eat it all herself. So she dropped some off for me to sell.’

‘Thanks Alf!’ Mika says. ‘That’s very helpful!’ Alf looks more puzzled than ever. Mika grabs Billie’s hand and the two of them dash out of the shop.

‘Andrea!’ Mika squeals, once they are safely outside. They dash around the corner where Alf can’t see them. ‘The witch lady!’

‘She’s not a witch,’ Billie corrects Mika. ‘Remember? She’s a friend of Jack’s mum.’

‘But does she have a strawberry patch?’ Mika says, a smile creeping across her face.

‘Hmm. I don’t think so,’ Billie says, trying to picture Andrea’s backyard.

Mika jumps up and down on the spot. ‘She might not be a witch but she could be a thief!’

‘You’re right!’ Billie says excitedly. ‘Come on! Let’s go find the boys!’