Alternate selves.

"Geez, look at this place." Jack O'Neill exclaimed loudly as they entered Holly's universe through the quantum mirror.
It was obvious they were on the mountain base, albeit a slightly differing one, however this one was dark with sirens wailing being the only sound that could be heard, sirens that warned of a breach of security. Debris covered the floor along with scraps of ripped clothing and pellets which had been shot from the guns of soldiers trying to protect themselves from the Goa'uld in a somewhat futile effort. Scorch marks covered the walls from the use of technology the humans were using to fight the Goa'uld and the Goa'uld the humans. It was eerily quiet and clear to the team the Goa'uld had advanced onto another part of the base a while ago The.team took out their weapons, not willing to take any chances and got ready to advance towards the Stargate.
"Wait a second." Daniel Jackson stated as they got ready to leave the room.
They turned to look at him.
"Somebody needs to stay here and guard the device and it's control. If we all go then this could get destroyed and we'd be stuck here. We need for someone to stay and make sure that that doesn't happen."
"Then I will stay." Teal'c told his friends. "If the Goa'uld return and my counterpart is not with them, I may be able to convince them to leave the mirror alone by taking on his role."
"You'll have a few problems doing that." came a pained voice behind them. "You were one of the good guys here, well before you were killed by Apophis for being a traitor."
They turned around to see a figure slumped in the corner, one who had been shot and was bleeding a considerable amount.
"Kawalsky?" Jack O'Neill asked instantly recognizing his late friends voice.
"I take it I'm dead in your world then." he told the team.
"Just a little." Jack answered in his usual sarcastic tone, going over to his friend who noticed Jack staring at his wound.
"I was caught in a fight with the Goa'uld. They got into the base just before Holly left this morning, been trying to take it over ever since. They haven't done as well as they'd hoped though cause everyone's been fighting back. It's not gonna be long though before... Half the bases population are dead, others are enslaved while the rest are in hiding or have been left to die on their own. It's not pretty."
"You should go get the Doc to take a look at you....if there's an infirmary left."
"It's a scratch, I'll be fine." Kawalsky assured them.
"Looks a little more than a scratch to me." Carter stated.
"Look I'm not here to argue. If you need anyone to look after the device I'll do it. The Goa'uld already think I'm dead, I suppose if they come back I'll hide this little beauty and play it. Go save our universe will ya, we've certainly run out of ideas...GO." he shouted snatching the device from Daniel.
"You're a good man Charlie." Jack told his friend softly before he and his team made their way down the coridoor determined to help Holly and her friends.

As they walked the eerie feeling about the base grew stronger. It was too quiet. There was nothing to be heard , no screaming or footsteps, just nothing..The only sound was the wail of the siren, and the team found the silence that came from no human life being apparent more deafaning than that.
"What the hell is going on here?" O'Neill shouted.
"Could you have done that much louder?" Daniel answered back.
"Cut it out you two." Samantha Carter told her friends quietly. "We're here to do something, lets just get on with it."
They carried on walking along the corridors which were now becoming distorted with the lack of light. Looking for their counterparts was proving just a little harder than they thought. It became just a little bit easier when Daniel tripped over a figure slumped on the floor. Shining a torch on to the wounded person he discovered it was his own counterpart though a little grayer and obviously hurt.
"So you're here to save the world huh." the injured man asked sarcastically. "I take it Holly got through the device all right."
"Yes she did, and she's fine. What happened to you?" Carter asked the older and alternate version of Daniel.
"Got electrocuted by one of those Goa'uld weapons on my way to the infirmary."
"You got shot on your way to the infirmary? Isn't that just a little bit strange." O'Neill asked.
"Not when your wife's down there it's not." he told them. "So you guys gotta plan?"
"Your wife? Shau'ri? She's here?" Daniel asked.
"No she's not. Unfortunately she died.. I got married again to somebody who I love very much. Look I asked a question." He continued firmly.
"Yes we have a plan." Jack O'Neill told him. "And we're going to need your help to execute it. We have to find your colleagues and get you guys through the Stargate."
"May I ask why?" came another voice from down the corridor.
A figure approached limping. Daniel shined his torch upon the approaching figure already recognizing the voice, knowing he wasn't a threat. It was an older, and balding version of Jack O'Neill.
"Sorry , I didn't mean to scare the guys who have come to save our world." he told them sarcastically.
"They have a plan Jack, lets hear them out before you turn into your usual bitter and defensive self." Daniel replied.
"Fine." he told them lowering himself to the floor.
"Look we know a race in our world who are enemies of the Goa'uld. A race who despise them and disagree with everything they stand for, as we do ourselves. We think they could provide you with ships, maybe even a fleet which could fight against the Goa'ulds own." Samantha Carter explained.
"The Asguard? yeah we met them. Thought they could help us too. Turns out they couldn't even scare off the whole fleet."he told them sarcastically.
"They tried their best Jack." His colleague told him.
"We don't mean the Asguard." Daniel explained. "In our universe we came across a race called the Tok'ra. Now they're kinda like the Goa'uld, they carry the same Goa'uld larvae inside them, but they're good guys who disagree with the Goa'uld ways. In our universe they've formed a resistance. Now we figure if we can get you guys through the Stargate to their home world using our coordinates, and you tell them what's going on..."
"Earth just might stand a chance." the younger Jack O'Neill finished. "The Stargate is still standing right?" he finished.
"Yes it is." the balding Jack O'Neill stated standing up with new found determination. "So you gonna cover us? or are we gonna do it the hard way?"
"We'll cover you old man. Wouldn't want you to slow us down now would we." the younger Jack told his limping older counterpart. "Lead the way."