"Nice lunch?" Holmes watched as Dr Watson pinned a map of Greater London to their living room wall. On it, marked in Irene's neat handwriting were the names and locations of each member of the Tandem Club.
"It was very good, yes." Watson replied. "We even had apple pie for pudding. Home made too."
"Lucky you." Holmes replied, surreptitiously sniffing at his shirt. He smelled like a hospital.
"And what did you find out on your cold, lonely trip to South London?" Watson had obviously enjoyed his afternoon and was determined to rub it in.
"Kaluza and his colleagues were working on an experiment. Something that went very wrong, or very right, depending on your point of view. The fire was meant to destroy their work but Kaluza smuggled at least part of it out of the lab and hid it somewhere."
"And that's what our grave robbers are looking for?
"It must be buried in one of those cemeteries, or at least someone thinks it is." Holmes flicked through the sheets of paper on the desk in front of him. Each sheet contained a short biography of the individual members of the Tandem Club. They didn't seem to have much in common, separate nationalities, different universities, different disciplines and the last man in particular seemed to be the odd one out. Michael MacLeod, Scotsman, cartographer. He had worked for the Ordnance Survey office during the war and in 1945, the year of Theodor Kaluza's fall from favour, he had been given the job of re-triangulating the whole of the British Isles, essentially, checking and re-drawing every map of the country. Irene would probably have some examples of his work tucked away in her basement files. But what was a cartographer doing hanging out in a club for science nerds and was it just a coincidence that William Hinton went on his grave robbing spree only two months after MacLeod had been buried? He opened his laptop and started typing. MacLeod's presence in the story bothered him and he needed to do some more digging.
Watson flopped down in to his favourite armchair and watched as his friend worked diligently on his computer. Pinning up the map had made his wounded shoulder ache and he flexed his fingers against the pain.
"Any idea what this experiment was yet?" he asked.
"No. Lestrade has cars posted at all the cemeteries tonight but we need more data." Holmes replied.
"Well, if the fire was a cover up by SOE maybe Mycroft can help." Watson suggested against his better judgement.
Holmes grunted.
"Even if he did know he'd deny it, or make me beg. Either option is not acceptable."
"So, we just wait?"
"You're waiting." Holmes replied, keen to bring the conversation to an end. "I'm thinking."
Irene felt light-headed. Her heart pounded in her chest, a cold sweat pricked the back of her neck. The envelope, which had been pushed through her letterbox an hour earlier sat on her kitchen table, empty. The CD which it had contained was now in her laptop, playing over and over again.
"Good evening Miss Adler." the anonymous voice was male, educated, the accent identified the speaker as Greek. "I apologise for the impersonal nature of this communication. If these photographs are any evidence it is my misfortune that we cannot meet face to face."
She scrolled through the images on her screen. Some of them were over ten years old, every one of them taken in a different place, all of them containing the same two figures: Irene and Sherlock enjoying a drink in a café in Cambridge, the two of them in a library in Berlin, at a museum in Edinburgh, sharing a water taxi in Venice after an overnight flight from Heathrow, Irene sleeping briefly with her head on Sherlock's shoulder.
The voice was continuing.
"I was sure that the problem of the Tandem Experiment would attract the interest of Sherlock Holmes and, whilst I feel confident that we will succeed despite his involvement, my employer has demanded an insurance policy and that is where you come in Miss Adler. The recovery of lost artefacts is your particular talent, a talent I am told you share with many members of your family. Enclosed on this CD is all the surviving information on the Tandem Experiment. Find and retrieve the formula for us before Sherlock Holmes does and your friendship can continue unhindered for now. Should he retrieve it first my employer has made it clear that drastic measures will have to be taken to relieve him of the prize."
Irene jabbed the Escape key on her keyboard, unwilling to see or listen to any more. For all these years, ever since Cambridge, someone had been watching them. The first name that entered her mind was Mycroft but this wasn't his style. He might be devious and manipulative, he might insist on calling her Yoko every time they had the misfortune to bump in to one another but he loved his younger brother and wouldn't threaten his life. He certainly wouldn't turn to her for help. But whoever it was they were thorough enough to have Holmes and perhaps even herself under detailed surveillance. It was no coincidence that the envelope had been delivered minutes after Watson had left. She needed to warn Holmes but from now on she couldn't risk contacting him directly or having him try to reach her.
Irene took a deep breath and pulled herself together. Rising from the kitchen table she moved through to her living room and retrieved the print out from her printer. If this was all the information available on this mystery they were in trouble. Just a few short paragraphs, a biography of a Swedish academic, an Edwardian physicist called Johannes Tandem. Irene had never heard of him or his work but she knew someone who might have. Father Marco Quillici, former head of the Vatican Observatory, now teaching at St Anthony's Catholic seminary in Chelsea. Walking through to her bedroom she pulled her overnight bag out from under her bed and began to pack. It was time to check in with the office.