It's been such a long time. I apologise so much… but here is the long expected Part 4 of A Study in Blue Boxes. VOA1 xx

Sherlock rose from his seat immediately 'how did I just let him walk out the door?' he shook his head more vigorously 'how did he just leave?'

John laughed 'Lestrade was right. He is a bit like you.'

Sherlock shook his head 'don't be stupid, John.'

John scratched his arm as he smiled 'but to be fair, that is something…'

'John!' Sherlock interrupted before Lestrade came wheezing into the room 'what?'

'You know you were talking about some blue box?' Lestrade asked holding the door open.

'Yes,' Sherlock said.

'Well,' Lestrade paused 'you had better come and have a look at this.' Lestrade began to walk out of the door with John and Sherlock closely following. They weaved through the corridors until they arrived at Lestrade's office where Lestrade passed Sherlock a mobile phone.

'Yes?' Sherlock asked.

'Watch it then!' Lestrade said.

Sherlock peered down at the phone and pressed the sideways triangle at the bottom of the screen. As soon as he pressed the button he heard what could have only be described as the sound of the universe as they watched an old 1920's style police box disappear from sight.

Sherlock's face immidietly lit up 'can you tell me where that was?'

'The woman who handed in the phone said she filmed it at Baker Street,' Lestrade said.

'Where we live,' John said.

'When did this happen?' Sherlock asked.

'About half an hour ago,' Lestrade said.

Sherlock look baffled 'but he was here with you half an ago.'

'If it is the same man then he must have had some help,' John said.

'Where is he now?' Sherlock asked 'has the blue box reappeared?'

'No,' Lestrade said 'but we can send out a public message.'

'Good idea,' John said 'if we can track his movement then we can find out what he wants.'

'No,' Sherlock said 'a man like this must have enemies. A man who can put the government on red alert and disappear, he must be running from someone. I say we try and keep this as small as possible. We don't want to be pulling out another bunch of lunatics from the woodworks at the moment.'

'So what do you suggest we do?' John asked.

'We wait until we see the blue box again,' Sherlock said 'Mycroft said he has been appearing around London an awful lot so I won't be long until one of sees him again and if we don't then it means whatever he wanted has been dealt with and nobody has died.'

'I know you, Sherlock,' John said 'it's not just about protecting the general public. It's the satisfaction of finding the answer. You won't let this go.'

'John,' Sherlock said 'I'm trying to show the heart you so often say I need.'

John shook his head 'do we even know who this man is?'

'He is The Doctor,' Sherlock said.

'Yes,' John said 'but Doctor who?'

'That's exactly what we need to find out,' Sherlock said 'and I am guessing our best bet is to find friends and family. John you start of by looking up as much as you can about The Doctor and blue boxes, Lestrade you look back a police records; try and find anything unusual – similar to today. I'm going back to Baker Street. I'll be back here in about an hour. Don't disappoint me.'