Spoilers: Hounds of Baskerville

31 in which our hero Sherlock conducting experiments and gets results he didn't expect.

Everything led back to the hollow. That was the only place Henry could be off to and the place where all the sightings were.

Well, except for John's sighting but that was mostly Sherlock induced.

It all started as a simple experiment. Sherlock had his legs up on the counter. Conditions were controlled. John was safe as he could be. Much safer than on London streets on any day of the week.

The sugar should have work by now. Approximately the same amount of time passed as when Sherlock and Henry saw the hound. That's why he started the experiment by the lights. Here there was no darkness to induce the state of anxiety so Sherlock used lights and sounds.

In the beginning, John didn't display much so Sherlock amplified the sounds and finally got John scared. Still, he just seemed alarmed but he didn't confirm the sighting. It was important that he sees the beast, that he believes he saw it.

Then it happened. John went into a full state of panic but his voice was too shaken. He sounded so out of it that Sherlock started to worry. He hurried to find John. Sherlock knew that the lab was safe but still. John's fear disturbed Sherlock, it was too big, his heart could stop from it.

Sherlock lit up the light and lifted the sheet. As he entered the cage he tried to see is John alright but John just ran out.

He looked around in the state of shock and Sherlock reassured him that he's safe.

"It's ok now, you're safe," he said.

"No, it's not," John yelled. "I saw it, it was there. I was wrong."

As soon as John said he was wrong Sherlock's worry disappeared. It was nice to be on this side of drug-induced delusion.

"Let's not jump to conclusions," Sherlock returned John's own words back at him.

John, of course, didn't appreciate them in his state of agitation.

"We have all been drugged," he quickly explained to John. "Can you walk?" he asked because John didn't look steady on his feet.

"Of course I can walk," he said already suppressing his emotions.

Sherlock accepted that. John could always function, no matter what the danger was, he just needed a goal. All Sherlock needed to prove his theory was to find the drug.

For that, he needed a microscope. The facility was full of them, but it was also full of suspects so Sherlock went to the only person that was disqualified from the list of suspects.

Dr Stapleton clearly wasn't their perpetrator. She was far too out right and focused on the practicality of animals to be involved with something so sinister as a hallucinogenic drug that covers up for a murder.

She cooperated by a slight threat that they would tell her daughter the destiny of her rabbit. No matter how cold Dr Stapleton thought she was, she cared enough for her daughter to get her a rabbit and then to remove it without disturbing her child.

Sherlock searched for the drug but the sugar was clean.

That was just wrong. John did suffer the delusion, he was still twitching from the severity of his fear. John in his clear state of mind feared almost nothing. Wearing the vest with explosives invoked just a slightly elevated perspiration, nothing more.

"I need to go to my mind palace," he said to Dr Stapleton.

He hated to think in the presence of strangers.

It took him a while but he finally found the reason why the acronym H.O.U.N.D. invoked such a strong sense of familiarity.

Surely, it was somewhere in Mycroft's hidden files through which Sherlock would browse quickly, unseen, barely seeing what's on the screen, just focused to collect data before Mycroft busts in and find him snooping through his things.

Sherlock looked at the picture of scientists who worked on the project and finally saw the cheerful scientist in the background. The Uncle Bob. Why were always those uncles who would get in and just do the damage?

The pretty therapist called John interrupting Sherlock's message but she just called to warn them about Henry.

Henry was running with a gun back towards the hollow and the cheerful scientist was lurking in the darkness waiting for him, knowing that it is inevitable for the boy to return to the site of his tragedy.

Sherlock drove through the darkness worried for Henry. Sherlock and John were influenced just briefly and they were shaken to the core by the fear and dread beyond understanding. Henry was drugged for months now.

They reached Henry just in time to prevent him from committing suicide.

Sherlock talked to him in his steady fast voice keeping his attention glued to himself.

"You couldn't cope. You were just a child. So you rationalized it into something very different."

John did his part walking in slowly and disarming Henry. Then Lestrade was there and it seemed they are fine but they weren't.

Suddenly they all started to see the monstrous hound. It was hard to tell yourself it isn't real when everyone saw it. Sherlock tried to reason with himself but his eyes showed him the hound.

Then he saw a man under the breathing mask. When he removed the mask, it was Moriarty but Sherlock was determined not to fear him.

"Not you," he yelled grabbing him but when he swung him out of the fog he saw that it was just their scientist, the one who was drugging them.

"The fog. It's the fog, the drug is in the fog," he said to others. "Aerosol dispersant."

The dog kept going at them and John and Lestrade shot it. When the dog was dead, Sherlock grabbed Henry.

"Look at it," he said knowing that he'll never be free of fear if he doesn't face his demons.

"Why didn't you just kill me," Henry attacked his uncle Bob.

"Because dead men get listened to," Sherlock explained to him something Sherlock knew by heart. "He needed to discredit every word you ever said about your father."

In that moment, he finally saw Moriarty's final game. He'll came after Sherlock, take away his credibility, make him the laughable item and then try to make him commit suicide. This was that play on the smaller scale but Moriarty won't be satisfied with an intimate stage like this one, Sherlock's fall will be seen by the world.

"He had means," Sherlock kept talking thrilled by his discovery. "Pressure pads, dosing you up every time you came up out here. Murder weapon and scene of the crime all at once," Sherlock laughed. "Oh, this case Henry. Thank you. It's been brilliant."

"Sherlock," John's warning voice stopped him.

"What?" he said confused.

"Timing," John whispered objecting him.

"Not good?" Sherlock checked did he understood it right.

"No, no," Henry said. "It's ok. It's fine because this means that my dad was right."

Henry talked resolving his long term trauma when the dog growled again. John shot the dog again and uncle Bob used that opportunity to run. He ran. They chased him but he got into the mind field and was blown away escaping the shame of justice.

It seemed to me that Sherlock was geniunly scared for John when he entered the cage eventhough he was the one controlling the experiment.

Also, the parallel between Henry and Sherlock's lost childhood memories is easy to see after watching 4th season.