"What are we looking for exactly?" John had followed Sherlock under the SOC tape across the door of the Security Guards office.

"Something that would make a grown man die of fright. Think John."

"Erm, an Intruder?"

"He was special services. Guarding something. I think he would be expecting an intruder."

"Something he wasn't expecting then? Why are you asking me? You obviously already know what it is and you're just doing this so you can remind me of how clever you are. "

"Are you grumpy? Come on John. You know how much I really like you to help."

"Okay. A ghost. Someone from his past he thought was dead. Who obviously isn't because there's no such thing as ghosts."

"Good. Or something that made him think he was seeing a ghost. Something that also caused his heart to fail."

"Well that could be almost anything. There are all kinds of toxins which can cause visual and auditory hallucinations and also induce heart failure in the right dosage; most of them would show up on the tox-screen. But there would be some kind of residue, smell, vomit, needle marks where it was introduced to the body."

"You are completely correct John. Excellent. Do you know of any toxins that can be introduced without the individual being poisoned realising?"

"I can think of one. Devil's Foot Root. It's a hallucinogenic. But if taken in a strong enough concentration it sends you mad, and it's from the same family of plants as Digitalis. So it would also affect your heart. The Shamen out in Afghanistan use it."

"How do they take it?"

"Sometimes they make it into tea, but usually they smoke it. A tiny little bit mixed in with other herbs and tobacco. It's like a sticky resin stuff." Sherlock was looking at John as though he was the most beautiful object on the planet.

"God I am so turned on right now John Watson." Sherlock flicked his scarf, bearing his neck. John gulped.

"Absolutely not. Not in a dead blokes office. There is a line you just don't cross."

"Am I coming up on it?"

"Look behind you Genius." Sherlock sighed. And continued his search of the office. He picked up a mug of cold tea and sniffed it.

"Does that smell okay to you?"

"Well its day old cold tea. It smells as well as can be expected. Oh look at this. He's got one of those USB Mug warmer things. Now if you want to get me something for Christmas you can get me one of these. You just plug it in and it warms up and keeps your tea hot. Brilliant." Sherlock smiled indulgently. John really liked gadgets. Then he got that look on his face that said a billion pieces of jigsaw puzzle had all clicked into place.

"The tea! Of Course!" He tipped the mug out into the bin and turned it over. On the base of the mug were faint traces of a sticky substance. Sherlock sniffed.

"Devil's feet I presume. The murderer smeared it on the mug and then it heated up when Mike Jones stood it on his Mug warmer. This tiny room would have been filled with hallucinogenic fumes. "

"He would have tripping his tits off. That's my considered medical opinion by the way."

"Exactly. And imagine in that altered state of mind he came out into the hall and saw a gang of masked men moving a dinosaur."

"That would probably be enough to give him heart failure. Yes. It would certainly do it for me I think."

"So that's how the Security guard was disposed of. But why kill him? Why not just tie him up and gag him? And still why steal a dinosaur?"

"Maybe they didn't mean to kill him. It's not like you can accurately predict how someone is going to trip out. Maybe they just thought it would keep him occupied in La-La land whilst they got Donald out of the way."

"But how?" Sherlock spent the next hour crawling around on the floor of the natural History Museum, getting tutted at by passing staff members who were obviously having a period of mourning for their missing Diplodocus. Suddenly he leapt to his feet.

"John! I know how they got it out of here!" And Sherlock was off and running, his scarf and coat billowing behind him in full sail. John grinned happily as he sped off in Sherlock's wake. No matter what happened he was getting some tonight!