The next day, there was another murder. Again, it was a man and again, his eyes were wide open. 'But there's got to be more,' said Sherlock as he peered down at the body lying on the ground. 'There has to be something else that links these two!' This murderer doesn't just choose his victims randomly. He wants to know something that these men knew! Think, John, what could both these men know that very few people know?'

'It could be anything: a secret they shared…'

'Not just a secret, an important secret. And probably dangerous. An important, dangerous secret that the murderer wants to know, and that these men knew about… Hang on, John, what were you saying again?'

'It could be anything?'

'No, after that.'

'Er – a secret they shared?'

'Shared,' said Sherlock thoughtfully. 'Maybe these men knew each other.' He turned to the dead man's wife, who was standing behind them, crying silently. She'd let them into her house after Lestrade had assured her she could trust them. 'Have you ever heard of a man called Steve Smith?'

She shook her head. 'N-no.'

'Are you sure? Could he have been a friend of your husband's?'

'N-no. I know all – all of his friends, but there's no Steve among th-them.'

'Oh,' said John, disappointed, but Sherlock asked another question.

'Was there ever anything strange about Craig?'

'Well, there was something… but it's probably n-nothing.'

'Tell me,' ordered Sherlock sharply.

'Sometimes he'd go away for an evening and he'd tell me he'd go bowling with his friends, but he forgot his key one such evening and I tried to call him, but he wouldn't answer his phone. So I called one of his friends but he told me he and the guys had never gone bowling.'

John gasped. 'That's the connection! They both – what, actually? What did they do?'

'I don't know,' said Sherlock. They left the house and walked through the city. 'But I'm sure it's why the murderer chose to ask them.'

'Maybe those times they were away, they met with the murderer and he threatened them.'

'No. He'd be upset if he was being threatened, but when I asked if there was anything strange, the woman didn't mention any strange behaviour of her husband.'

'That's true. But maybe they did meet up with the murderer those times, but he didn't actually threaten–'

'Did you notice his wife's strange behaviour?,' interrupted Sherlock. ' Another connection.'

'What d'you mean?'

'At first it seemed like she was crying, but when she told us about the bowling thing she stopped. The crying was fake. She didn't care about her husband at all.'

'Blimey,' said John. 'Both men had a difficult relationship with their wife. D'you think their wives killed them?'

'Don't be so silly, John,' Sherlock said, quickening his pace.

'Why not? In both cases, the wives were angry with their husbands!'

'And why were they angry?'

'How should I know?'

'Because of them going away without telling their wives, of course! Martha was angry because Steve went away a lot. This was because of Leslie, but also because of this other thing, whatever it is. The woman we just spoke to tried to sound casual, but when she told about her husband going away her voice sounded accusing.'

'Yeah, she was angry so she killed him.'

'It's not that simple. The murderer wanted to know–'

'–where her husband went those times!'

'No.' Sherlock rolled his eyes. 'What about the note that was written by the murderer? It was clearly one person who killed both men.'

'Maybe the two wives helped each other?'

'You know, it's actually a really clever theory.'

'Thanks!'

'But it's no more than that, a theory. The woman said she didn't know Steve Smith, and she wasn't lying. She's a really bad liar.'

'You immediately knew the woman was pretending to cry, didn't you?' asked John, sounding impressed.

'I did.'

'So what d'you think the murderer is after? A weapon?'

'Would he need a weapon, though? He can already kill in a way that leaves no traces.'

'Perhaps a more effective weapon.'

'Yes…possibly. I know one thing, though: I don't want him to find it.'