Billie stands on the footpath, staring after Edwina. She knows she really should go home. She’s not sure what time it is but when she looks up at the sky she can see one, two, three pale stars have appeared. Billie is not allowed out after dark.

But it’s not dark yet. Billie tells herself. And I’ll only be a few more minutes. I have to find out what Edwina knows! I can’t go home now!

She takes a big breath and runs after Edwina. She catches up just as Edwina reaches her front door.

‘Wait!’ she says. ‘We’re looking for a time capsule. Mrs Singh told us about it. But you have to promise not to tell anyone I told you. My friends would kill me!’

Edwina smiles. ‘I knew it! I heard you talking in Mrs Singh’s office.’

‘What? You were listening to us?’ Billie says, crossly.

Edwina blushes a little. ‘Only because I needed to, to solve the mystery,’ she says. ‘Sometimes detectives have to do that, right?’

Billie is still a bit cross, but Edwina has a point. After all, the SMC has had to listen at doors before too!

‘I have something in my bedroom that I think will help you find the time capsule,’ says Edwina. ‘Come with me!’

Billie follows her into her house. She can hear a TV playing loudly and someone talking at the end of the hallway. Edwina leads her into the first bedroom on the left. She points at her window. It has a clear view across to the school grounds.

‘Wow! You can see everything from here!’ Billie says, amazed.

‘It’s a good spot for spying,’ Edwina says cheekily. ‘I’m a spy as well as a detective.’

‘Me too!’ says Billie. ‘Alex says they’re not the same thing but I think, really? What’s the difference?’

‘Right!’ Edwina grins. Billie grins back.

Edwina opens a drawer in her desk and pulls out a rolled up piece of paper.

‘What’s that?’ Billie asks.

‘This,’ Edwina says dramatically, ‘is the clue you’ve been looking for.’

Billie hovers next to Edwina as she unrolls the paper. ‘Is it a map?’ Billie asks. ‘Of a building?’

‘Not just any building,’ Edwina says. ‘The school building. This is a photocopy of the original plans. Look, it says here: 1923. The school is nearly a hundred years old. Can you believe it?’

‘Wow!’ Billie says. ‘That’s older than my Nanna. And she’s old!’ Then she frowns. ‘Mrs Singh told us that the plans were lost ages ago, though. How did you find them?’

‘My mum’s an architect,’ Edwina says. ‘She was in charge of renovating the school before I was born. The plans must have been lost then, but luckily Mum found this copy when she was tidying out her office the other day. She thought I’d find them interesting.

And when I overheard Mrs Singh telling you about the time capsule, I knew I had the perfect clue to help solve the mystery!’

While she is talking, Edwina unrolls the map across her desk. She and Billie lean over it, staring down at the pale lines on the page.

‘That’s the front entrance to the school,’ says Edwina, pointing. ‘And there’s the main corridor.’

Billie nods. She finds the map a bit hard to read.

The school on the map looks much smaller than it is now. But now that Edwina has pointed out the front entrance, she starts to recognise some of the other buildings.

‘So that’s the music room, right?’ says Billie.

‘Yep,’ says Edwina. ‘And that’s the library.’

‘What’s that, then?’ Billie asks, pointing to a small empty space between the library and the music room on the map.

Edwina frowns. ‘Hmm. I don’t know. It looks like a big cupboard, maybe. But there are bookshelves all along that wall in the library, and there’s no door on that wall in the music room. I can’t believe I didn’t notice that before!’

The two girls look at each other, excited. Billie can tell they are both thinking the same thing.

The space looks like the perfect place to hide a time capsule!