On Saturday morning, Barry arrives at STAR Labs around ten o'clock. While Barry does not technically need to show up for his internship on weekends, he's accumulated a bit of a backlog as a result of working down in the Cortex. More importantly, they were on the verge of activating the tachyon prototype – it would happen on Monday at the very latest – and Barry wouldn't be content to idle his weekend away at home.

He is also curious whether Dr. Wells had really showed up at the séance last night, but all thoughts of asking the ghost directly fly from his head when he hears the sounds of furious shouting as he walks down the hallway to his lab.

"Don't tell me you have no idea how this happened, Ramon!"

It sounds like Hartley, though Barry has never heard him raise his voice before. Alarmed, Barry pushes his way through the half-open door.

"Well, it's the truth! I don't know how – " Cisco stops when he sees Barry.

Hartley turns and sneers, "Come to blunder blindly in and offer your no-doubt enlightened opinion, Allen?"

"No, I just – "

"Then stay out of it!"

Barry turns to Cisco. "What happened?"

"Hartley's rats are dead. For some unfathomable reason known only to The Chosen One, he blames me."

"Who else is constantly lurking about at all hours, and will not give a straight answer when asked what he is up to? Who bears a personal grudge against me, and seeks to undermine my work? Don't play me for a fool." Hartley's face is blotchy with emotion.

"Okay first off: you only wish you were my nemesis, and secondly, even if you were I wouldn't go after your animals. That's sick and wrong. I liked your rats a lot more than I like you and they didn't deserve that."

Barry steps between them, hoping to diffuse the situation by breaking Hartley's line-of-sight. "How did the rats dies, Hartley?"

Hartley's nostrils flare, and his response is sharp and clipped. "Cannibalism."

Barry starts picturing what that means, a writhing mass of rats consuming each other, teeth and claws and fur and - and he immediately shuts down that train of thought. Still… "How can you possibly blame Cisco for that?"

Hartley somehow manages to look down on Barry despite the fact that Barry has several inches on him. "I can think of a number of ways he could have managed it; stress, drugs - the exact method does not matter."

"Look, as someone studying forensic science, I can tell you the method does matter. You like Latin; try modus operandi on for size. Or better yet, consider 'means, motive, and opportunity.'" Barry ticks off. "You need to establish all three before you can determine guilt – "

"Spare me the lesson!" Hartley picks up a beaker and looks willing to throw it. Deciding that this is not a rational argument that can be won, Barry grabs Cisco's arm and bodily drags him from the lab. They make it halfway to Barry's lab before they realize they aren't been chased, and slow down to catch their breath.

"You doing okay, man?" Barry asks.

Cisco jerks in surprise; he must have been lost in thought. "Yeah, yeah. Just… crazy what happened to his rats, you know? This was so not how I planned on starting this day." He brightens visibly, "Oh and what I day it will be! I got so much done last night – today's the day. The Big One."

Barry stumbles but regains his footing quickly. "What, really? I can't – wow! That's… Cisco, this is incredible!" He's ready to follow Cisco down to the Cortex before he remembers his reason for coming to STAR Labs. "I still have some catching up to do in my lab before I can join you – things I've put off for long enough. Don't turn it on without me!"

Cisco clasps his hand to his heart solemnly. "That might be asking too much, my friend."

Barry laughs and claps him on the shoulder before turning down the corridor that would take him to his own lab.

Two hours later, he's made a pretty good dent in the number of samples he needs to run and is feeling pleased with himself, when Iris suddenly bursts into his lab, looking harried.

He startles badly and accidentally knocks his mug of coffee off the lab bench. "Iris! What are you doing here?! You're not supposed to be here!"

"You weren't answering your phone. Barry – "

"If someone sees you – "

"Barry! Listen! We've got more important concerns right now. Where's Cisco?"

"Cisco? He's down in the Cortex, getting everything ready." He grins widely. "We're going to turn it on today!"

Iris blanches. "Oh no. We have to stop it!" She grabs his arm and tries to drag him out the door, but Barry digs his heels in and refuses to move.

"Iris! Iris, slow down and explain, or I won't be able to help you."

"Barry, Harrison Wells isn't who we thought he was, and I don't think that machine you've been building does what you think it does either."

Barry doesn't budge (Iris keeps tugging regardless). "I'm going to need a little more than that to go on, Iris."

"He didn't die of a heart attack. He died trying to summon a demon, and he succeeded. Eobardthawne, the demon, crushed his heart, and has been masquerading as his ghost ever since."

Barry blinks. "Okay, wow. That's… really not what I expected you to say. Do you have any, any proof? Or something?"

"I spoke with his daughter; I listened to his dying words. It all adds up. Don't you see? I-M-P-O-S. Not 'impossible,' imposter. Somehow we managed to contact the real Harrison Wells and he tried to warn us before he got interrupted."

"That's a pretty big leap, Iris, how do you know you're reading it right?"

"I'd say the bloody message on my wall after the séance telling me to 'stop looking' is a pretty good clue, wouldn't you say?" she snaps.

Barry feels as though all the air has been sucked out of the room. Someone – something – was leaving bloody messages for Iris? That didn't sound like the Harrison Wells he knew, but it did sound like something a demon would do.

"What can we do about a demon? A demon, seriously…" he supposes it isn't too great a leap to go from ghosts to demons, but his rational side still rebels against the idea.

"Salt helps against most spiritual entities. I don't know much else; I was focused on researching ghosts."

"… Does it have to be table salt, or will any salt do? Because we've mostly got sodium ethanoate and other buffer salts in the lab…" Barry offers tentatively.

"I honestly have no idea, but something's better than nothing."

Barry hurries to the right shelve and returns with a half-kilogram jar of ammonium chloride. Iris is visibly trembling and he tries to reassure her. "I know we need to get to the bottom of this, but I don't think we're as pressed for time as you believe. Cisco's just fiddling with last-minute details; he wouldn't turn it on without me."

Iris looks him straight in the eyes. "Are you sure? Are you absolutely positive?"

Barry opens his mouth to affirm, but hesitates. It's true that Cisco has become increasingly distant, increasingly focused on the prototype to the exclusion of all else. If Wells really is some sort of demon, Barry wouldn't put it past him to have some sort of malignant influence over them, over Cisco in particular – Cisco, who has spent the most time in his company, who has invested the most, given the most of himself to the project… Barry's heart skips a beat and a knot forms in his throat. Cisco has poured his heart and soul into the project, and what if that has repercussions?

Iris is still waiting for an answer. He meets her gaze head-on. "You're right. We need to hurry."

They race down the hallway, throwing caution to the wind.

[*hssssss*] Journal log entry number two-thirteen. Tessie - I'm coming for you. Soon. I know it sounds impossible, but I swear it's true. I've, I've found a way. I can't stop thinking about you, Tessie. Just earlier today I remembered the day that I realized I wanted to spend the rest of my life with you. It was my fifth and last week of gunnery school, and we were flying a drill at night - you were far ahead of us, towing the target. But there was a malfunction in your aircraft, and you needed to land in a field. We didn't know that, not at the time, just saw that you disappeared from our radar.

Panic. I abandoned my post and I seized the radio from Snowden; he'd made a mess of the whole system, we couldn't hear anything. And I could feel the fear rise in the back of my throat and something else rising also, some dark instinct inside me about what I would do to the ones responsible, the things I would do... unspeakable things. And it was in that moment that I realized, for certain, that I would do anything to get you back in my life.

We barely knew each other outside of drills, but when I thought you were lost, that was when I knew that you were the only one for me, the only one I could ever be happy spending my life with.

I'm coming for you, Tessie, and I'm going to get you back.

[*hsssssss*] [*sound of heavy breathing*]... I have begun a new undertaking. I hope, I hope… well. That should be readily apparent. And by readily apparent, I mean real fucking obvious. [*clunk.{2}*]

[*hsssssss*] journal log entry… whatever number. Fuck it. The book I received from Russell Glosson has been very informative, though my knowledge on the subject is still incomplete. I might have to make use of his services a second time to procure the necessary tome. I shall begin with…

* … It has now been… three hundred and eleven days since you were taken from me. Progress continues apace, though I have had to revise my initial thesis. It has become clear to me that there is no reason to think that the Subject should fear one denomination over the others. Mankind's philosophies are flawed and mutable, and I have concerns…

*…The fact that counter-measures vary so widely between cultures tells me that there must be something else at work, some other common factor, some commonality that as yet eludes me…*

*… I believe I have found a suitable subject. Its name is Eobardthawne. I will attempt to make contact next week, when the moon is in the optimal position…*

[*hsssssss*] New entry. The date is October 7th, at two-thirty-six a.m. Everything is set. Tessie, this is the moment. After years of research, I am ready to bring the Subject forward. I've prepared a containment circle that will prevent it from escaping and bind it to my will. All that remains is the incantation… [*sound of a throat clearing*]

Tibi gratias agimus quod nihil fumas, Eobardthawne! By the constraints of the circle, the points of the pentacle, and the chain of runes, I am your master! Credo Elvem ipsum etiam vivere! Eobardthawne, as the one who named you, I bind you to my will!

[*…hsssssssssssssss…*] [*thump*]

No! Don't - ! I command you! D-don't come any closer – You can't – aaAARGK- !

[*…hsssssssssssssss…*]

[*clunk.*]

A/N: Demon-summoning incantation brought to you by The Bartimaeus Trilogy and The Spectacular Spider-Man!