As much as you don't trust him, you have to admit Jack has never really done anything against you in all the time you've known him. If anything he's always attempted to be friendly. Is it possible you've just been an asshole to him, for no good reason?

Probably, but it wouldn't be the first time and that's all in the past. You take the bottle and down its contents.

"(BURP!) I don't feel any different."
"Oh you will trust me."
"I've put more than enough trust in you already, better not be trying anything Jack, because I swear I WILL get my revenge on you, if this is a fucking trick!"
"Not a trick, everything I've told you is the truth, you'll see."
"Yeah, we'll see."

When you enter the arena area, it's just a big empty white room with another door on the other side of it. High above you can see Henry on an upper floor with a clipboard behind some glass. He waves to you and speaks into a microphone.

"Okay Wolf, we're going to start off slow, this subject hasn't been injected with as much of the formula so I'm guessing you shouldn't have any problems with him. Try not to kill him though, since we DO want some of them to survive!"
"No killing eh? Well I suppose there's a first time for everything, alright Henry, send in the victim."

No sooner has the human entered the room, and you've already run up and drop kicked him in the face! You don't allow him to get back up, and end up breaking one of his legs by totally destroying his knee. He's in extreme pain and expresses it vocally.

"Damn Wolf! What the hell!?" Henry shouts.
"Hey you said not to kill him, you didn't say anything about not breaking bones."
"Alright, drag him out, and bring in the next one."

This goes on for the next five fights. If the subjects are supposed to be getting tougher, you haven't noticed. All you've notice is a severe change in the subjects, mainly being bigger and more vicious, they're starting to not even resemble humans anymore, and in fact they resemble "Mr. Hyde" but even more out of control. But you haven't even broken a sweat during all of this, it's like you're in your prime again. It must be Jack's formula. Looks like he didn't lie. You look up where Henry is located and you notice he seems to be ranting and yelling at Jack. He addresses you again.

"How are you doing Wolf?"
"Great! I haven't felt this good in years!"
"Hmm, well I guess I haven't been trying hard enough! Wolf, I'm sending three of them in there, try to beat that!"
"Hey, you're supposed to be testing their fighting skills not mine."
"No Wolf, I'm supposed to be KILLING you, but you're too fucking stupid to die properly! Well that ends now!"

Looks like Jack was telling the truth about that too, you attempt to leave the way you came in but, a solid metal door slides from a hidden panel to block your way. Even your increased combat abilities can't make more than a dent in it. Henry then begins to laugh maniacally and three lumbering hulks come through the opposite door all intent on doing you massive harm.

However, you don't have any fear about this situation, you're confident that you can take them and you do just that! You're literally a whirlwind of fury and violence. Bones are broken, flesh is ripped, faces are bitten and balls are stomped and happily none of them are yours. As you stand over the three large mutilated corpses you look up at the observation area and see only Jack standing there to address you.

"Hey Jack! Let me outta here, I got a score to settle with that fucking pussy Henry!"
"Uh, Wolf, you might want to prepare yourself, Henry said he's coming down to handle you himself."
"What as Mr. Hyde? Pfft! Yeah, I'm really worried. He's nowhere near as vicious as these fucktards were. I had to bail him out of most of the fights he started in the past. Sure he looked scary, still couldn't fight worth a shit though."

Suddenly a very large figure smashes through the wall opposite you, its Mr. Hyde and he's a LOT bigger and uglier than the last time you saw him. He's easily larger than the last three subjects you just put down.

"WOLF!!!" he bellows.

Okay somebody just overdosed on the "formula".

You escape

Even with your renewed "youth", you know you're not going to be able to take Mr. Hyde, not head on at least. You still need to get the hell out of here though and he's blocking the only exit, but you have a plan. Mr. Hyde predictably charges at you, and puts his giant fist through the wall behind you, collapsing most of it when you dodge out of the way.

Well there was your plan! When he unsuccessfully tries to hit you again, you roll out of the way and run out the opening Mr. Hyde just provided for you. You quickly take a few bricks and chuck them at Mr. Hyde's face when he attempts to squeeze through, of course that doesn't do anything except causing a few gashes and making him madder.

"YOU DIE TODAY WOLF!" he says collapsing more of the building in an attempt to get you. You just realized you're underground, if he continues with this destruction he's going to end up burying the both of you. You make your way to the elevator with Mr. Hyde in pursuit.

When you get to where the elevator is in sight, you see Jack with a briefcase, busily fiddling with the buttons, he turns to face you.

"Wolf! Watch out behind you!" he yells pointing in your direction.

You immediately dive to the floor

You don't think you just act and dive face first in the floor and roll attempting to avoid whatever Mr. Hyde has just thrown at you. The only problem is, he didn't throw anything; in fact he's still trying to squeeze through the corridor that's just a bit too small for him. Meanwhile you were rolling on the floor; Jack nipped inside the elevator and closed the door!

"SONOFABITCH!" You shout and quickly pry the doors open with all your might, but the elevator is already on its way up. Fortunately there is an emergency ladder on the side you can still use, or if you want to risk it the elevator has only just started to ascend, you could grab on to the bottom of it and take it up.

You grab the bottom

You jump up and grab the bottom as the elevator doors snap shut behind you. You hold on for dear life as you hear the building shake from Hyde destroying yet another load bearing pillar no doubt. The elevator is shaking as well which does concern you since if it suddenly starts to drop, you're going to be in a BAD position! As you dangle high above, you look down and see the elevator doors you came through being smashed through. Hyde sticks his head in first, then his massive body, and looks up, he sees you.

"DIE WOLF!"

His single mindedness on your death causes him to start digging his massive fingers in the shaft walls to climb after you! To make matters worse the elevator has just stopped, you hear Jack cursing above you. As you look up you notice a service panel on the bottom of the elevator. You could either open and go through that, or attempt to leap to the emergency ladder.

You leap for the ladder

You leap for the ladder and just barely make it from your awkward position. Hyde is still in pursuit and closing fast. When you start your ascent, the see the figure of Jack jumping on the ladder just above you, he must've used the service panel in the roof of the elevator to escape. He must've left the briefcase behind in the elevator too since he's not carrying it anymore. He looks down and pulls out a pistol. He fires several times, but fortunately only hits you in the arm. Unfortunately those bullets are silver and it fucking hurts like hell!

"Argh! Shit! I should've known not to trust you, you goddamned invisible bastard!" you yell.

Jack stops firing at you and then starts firing at the main elevator cord hitting it. The elevator is now dangerously dangling by a weakened cord. You quickly climb past the elevator before it falls which it inevitably does. You're safe, but Mr. Hyde isn't so lucky. The elevator drops at a good speed that even he can't stop in his position and knocks him off his shaft climb. Hyde makes a deafening roar as the elevator crushes his body when they both hit the bottom. You don't know if he's dead yet, but he soon will be, in any case its one less problem to worry about.

You continue your ascent after Jack, who is now at the top, trying to open the elevator doors. Too bad for him, he doesn't have enhanced strength like you and is struggling to open them up, while still balancing on the ladder.

"Ha ha, should've used your own formula Jack!" you say and grab his leg, digging your claws deeply in.
"Arrrgh! Let go you mangy dog!"
"You shouldn't have double crossed me Jack!"
"I can see my formula's made you stronger than I thought, I'll have to make a note of that after I put an end to you!"

Jack pulls out his pistol again which was a big mistake, as now he's not holding on to anything and is merely balancing on his legs, one of which you're holding on to…

You wrench the leg you've dug your claws into and pull hard, causing him to fall off.

"NOOOOOOOOO!" he screams as he falls into the dark shaft to his imminent demise.

You continue your escape by prying the elevator doors open and crawl through panting heavily. You lie face up on the ground for awhile just resting. You think the effects of the formula are wearing off. Too bad, you liked feeling "young" again. You do realize the folly of going against your instinct though; you knew you weren't just being an asshole to Jack for all these years for no reason. You knew he was shady. He might've been telling the truth about Henry, but he was just using you as a "subject" just to test his invention and to hopefully kill Henry in the process. Oh well you came out alive and they're both dead, you won. Though one thing pisses you off.

"Fuck. The money's buried down there." You say to yourself.