They found themselves back out on the street. Horse-drawn carts clattered along the dirt track, and men strode about in old-fashioned suits and hats. Clearly they were back in the past … but the place seemed different from before.

‘What is it?’ Martin wanted to know. Tommy frowned, trying hard to work out what had changed. Then it came to him: the air was fresh and sweet, not sharp with chimney smoke as it had been on his last visit. And the trees that lined the street were no longer bare, but bright with red and yellow leaves, and the sun shone gentle and warm. When he had come back before, it had been almost winter; now summer had only just ended. He had returned at a different time of year. Maybe even a different year.

How long had passed? Tommy wondered. It couldn’t have been long; the shops on each side of the road seemed much the same.

‘Martin,’ he said. ‘Check your phone. Let’s see what the date is.’

Martin pulled his phone out of his pocket and woke it up. He jabbed at the screen a few times and frowned. ‘It’s gone weird,’ he said. ‘No internet.’

Tommy sighed. He hadn’t thought of that: mobile coverage probably wasn’t great back in the nineteenth century.

As Martin tucked his phone back into his pocket, Tommy saw a familiar face.

‘Mr Bruun!’ he cried. Dragging Martin after him, he ran up to the man who was stepping out of the bakery.

‘Tommy Bell!’ the man replied. ‘Good day.’

Tommy introduced Martin. He was almost too afraid to ask how Ludwig was; what if he was in jail? But the old man brought the subject up himself. ‘You must come and see my boy, Ludwig,’ he said. Tommy exhaled in relief. So he wasn’t in jail, then. But Ludwig’s father went on: ‘He iss very troubled, my boy.’

The boys followed Mr Bruun down the road to his home. It was a neat little timber cottage with a verandah and a chimney and a pretty garden. Mr Bruun led them inside and into a cosy but dim little lounge room. In the shadows, a young man rose to greet them. It was Ludwig. Tommy was shocked to see how he had changed: his smooth pale cheeks were now bearded, and his face was paler than ever. There were dark smudges under his worried blue eyes.

His greeting was friendly but his voice was tired. ‘It’s been a long time, Tommy,’ he said.

‘Mmm,’ Tommy replied. ‘Remind me … exactly when was the robbery?’

‘Eighth of May, 1869,’ he replied without hesitation. ‘Almost three years ago.’

Three years! Tommy wondered what had happened in all that time.

‘I suppose you heard that they arrested me,’ Ludwig said, and Tommy nodded. ‘The police thought that I’d stolen the gold and made up the whole story about the armed robber. They also arrested my friend the schoolteacher, James Simpson.’

‘But why?’ Tommy asked. ‘Why would they think you did that?’

Ludwig shrugged. ‘I suppose my story was a bit confused. I was so terrified! I got a few of my facts muddled up when I was telling the police about it. There were no rope marks on my wrists so they didn’t even believe that I’d been tied up. And the note – remember the note? They said that the writing looked like James Simpson’s. They thought we cooked up the whole thing so we could get money from the bank and blame it on Scott. Why would I do that? I had a good job; I didn’t need to steal money! He’s the one who needed money!’

Ludwig was pacing around the room and his pale face had flushed a deep red. He clutched at his hair, making it stick straight out in straw-like spikes. Poor Ludwig, Tommy thought. He’s a mess.

Mr Bruun hushed his son and told him to sit down.

‘The case went to court,’ Mr Bruun said, pouring Ludwig and the boys cups of tea. ‘But zey found my Ludwig not guilty.’

‘Well, that’s great, then!’ Tommy cried, and Martin agreed.

‘But it iss not over,’ the old man continued. ‘My Ludwig hass suffered terribly. Hiss reputation has been spoiled. Ze man who did ziss to him must pay for it!’

Just then there was a knock on the door.

‘Ah,’ Mr Bruun said, as if he had been expecting a visitor.

He marched to the door and came back with his guest. The newcomer was snappily dressed in a suit and waistcoat with a silver watch-chain across his chest. He had a thick moustache that was waxed to a point at each end.

Mr Bruun introduced the stranger. ‘Zis is ze private detective zat ve have hired to investigate ze crime,’ he told the boys. ‘Hiss name iss Mr George Sly.’

Tommy held back a snort. A private detective called Sly? He tried not to meet Martin’s eye; it would be rude to laugh.

‘Mr Sly hass discovered many evil things about Captain Moonlite.’

The detective sat down, sipped at his tea, and began the story. George Scott, he told them, had been furious when the court had freed Ludwig. He had accused Ludwig of damaging his reputation.

‘He came to my house!’ Mr Bruun interrupted. ‘He came and threatened to horsewhip my boy if he did not apologise! Imagine that! He expected my Ludwig to apologise to him!’

Mr Sly waited for Mr Bruun to calm down before he went on. ‘But the people of Mt Egerton trusted Ludwig more than they trusted Scott. He feared that the law would get onto him, so he left town.’

Mr Bruun snorted again. ‘Sailed to Fiji! Lived ze high life: parties, drink, travel!’

‘It’s true,’ Mr Sly nodded. ‘He spent up big. He spent more than he had, in fact; he paid with some forged cheques.’

‘And then,’ Ludwig cut in, ‘then he went to Sydney and sold 129 ounces of gold!’

Tommy and Martin gasped.

‘Now, I ask you: where did he get that gold?’ Mr Sly went on. ‘From robbing Ludwig’s bank, of course!’

‘Where is he now?’ Martin asked.

‘He was arrested for the false cheques and he spent 16 months behind bars.’

‘Some of it in the lunatic asylum,’ Ludwig muttered.

‘That is correct,’ Mr Sly said. ‘He pretended to be mad in order to escape jail. But he didn’t last long there; they could tell he was faking. The superintendent said that he was …’ Mr Sly pulled out a sheaf of paper from his pocket and placed a pair of glasses on his nose. Then, reading from the paper, he finished, ‘… said he was “an artful designing and unprincipled criminal ready to join in any scheme of fraud or ruffianly violence that had a chance of success.”’

‘Blimey,’ said Tommy.

‘But he hass still not paid for ze bank robbery!’ Mr Bruun cried.

‘I am gathering evidence,’ Mr Sly said, ‘to convict him.’

‘What about the gold?’ Tommy asked. ‘Isn’t that enough to convict him? How did he have gold to sell? It must have been the gold that he stole from the bank!’

Then Tommy remembered the red neckerchief. He pulled it out of his pocket. ‘And this neckerchief! Moonlite was wearing it on the night of the robbery!’

‘A neckerchief?’ the detective waved his hand. ‘That proves nothing.’

‘You could get it DNA tested,’ Tommy suggested excitedly.

He’d heard all about DNA testing on a science programme on the TV. DNA, he knew, was the stuff that made up your cells; it was the stuff that made you you. Everyone had different DNA. If scientists found some of Andrew George Scott’s DNA that had rubbed off on the neckerchief, they could prove it was his, and Ludwig had already told him that the robber wore a neckerchief exactly like this one, and …. But the men were staring at him as if he’d gone mad. Martin frowned and shook his head. Idiot, he seemed to be saying. No one had even heard of DNA back in 1872.

‘What is this DNA test?’ Mr Sly asked.

‘Nothing,’ Tommy said, blushing. ‘Never mind.’

Mr Sly shrugged, clearly deciding to ignore Tommy’s strange remark. He leaned in to look hard at Tommy. ‘We need more evidence,’ he said. ‘We haven’t found the gun.’

Tommy shoved the neckerchief back into his pocket. He thought hard.

‘Can you think of anything, Tommy?’ Martin urged. ‘What can you remember?’

Tommy closed his eyes and tried to remember the events of that night. The glint of the moonlight on the gun, the boots crunching on the gravel. The voices in the schoolroom, the light of the match, the note. Captain Moonlite rushing past him out the door, the gun in his hand, striding down the moonlit path … suddenly, Tommy sat up straight. He saw it again: the armed robber hurrying down the road in the path of the moonlight, then veering off and hunching over a big dark shape by the side of the road. A splash.

Tommy leapt to his feet. ‘The well!’ he cried. ‘Have you searched the well?’

‘The well!’ cried Ludwig. ‘Of course!’

Ludwig and his father jumped up and rushed to the door. The private detective held them back

We have to do this properly,’ he said. ‘Fetch the police.’