(This does contain spoilers, but considering it aired 15 years ago you should have had time...)
OVERVIEW:
The weeks following SG-1's intense adventure keep the SGC busy as wave after wave of their new found enemy attempt to penetrate the Stargate's shield. Little does the team know, but someone has already gotten through.
REVIEW:
Personally I liked Enemy Withing, I thought that for beginning Stargate is was a good episode showing how the Gou'ld can infiltrate almost anywhere, no matter how many weapns you point at the Stargate, and also gave more light to how when it is required, Teal'c will do anything necissary to protect the one people who actually showed him trust and support. This reappears several more times throughout the series.
It was a little annoying that the infiltrator turned out to be Kawalski but only because he (Other than Daniel and Jack) was the last Alumni character from the original movie.
All in all, this episode is just another reason why Stargate SG-1 is a really great piece of work, from the writers room, to the actors. When it comes to O'Neill's humor or the serious but caring Teal'c everyone keeps the fun going and suspsense up.
OVERVIEW:
The weeks following SG-1's intense adventure keep the SGC busy as wave after wave of their new found enemy attempt to penetrate the Stargate's shield. Little does the team know, but someone has already gotten through.
REVIEW:
Personally I liked Enemy Withing, I thought that for beginning Stargate is was a good episode showing how the Gou'ld can infiltrate almost anywhere, no matter how many weapns you point at the Stargate, and also gave more light to how when it is required, Teal'c will do anything necissary to protect the one people who actually showed him trust and support. This reappears several more times throughout the series.
It was a little annoying that the infiltrator turned out to be Kawalski but only because he (Other than Daniel and Jack) was the last Alumni character from the original movie.
All in all, this episode is just another reason why Stargate SG-1 is a really great piece of work, from the writers room, to the actors. When it comes to O'Neill's humor or the serious but caring Teal'c everyone keeps the fun going and suspsense up.
While Ferretti, gets taken to the infirmary, Jack asks what it is. Hammond informs him it is an “iris”, made of pure titanium. Hammond wants to know what happened on the planet, and Jack tells him base camp was attacked while they were off looking around.
Back on Earth, Jack checks on Ferretti, then takes Daniel home. 
They discuss Abydos, Sha’re and Jack’s son, who died right before the first movie. A little later, we see a group of women waiting, including the female Airman from the beginning of the episode. 
She’s taken to see the Ra look-a- like, who says that she could be the vessel for his queen. But the “queen” rejects her, and she is unfortunately killed. 
A doctor comes in a informs them that Ferretti is awake. He manages to remember the symbols dialed by the aliens and types them on the computer. 
They head through the gate, arriving at an unknown planet on the other side. They set up camp, making it a defensible position in case they are attacked. Back in the unknown complex, Sha’re is taken next. Like the Airman, she is taken to meet the “queen”. 
But unlike last time, Sha’re is acceptable to her. The “queen” burrows into the back of Sha’re’s neck, taking her body as her own. 
They take SG-1 to the town, called Chulak. 
There, they are treated to a feast, which is interrupted when “Ra” and Sha’re, now possessed, enter the room. 
Daniel jumps up and attempts to communicate with her, but is knocked back by “Ra”. Jack raises his weapon, but when Sha’re jumps in front of Apophis, he lowers it in surprise and is knocked unconscious. 
Daniel figures out that it isn’t Ra that they are fighting against, it’s Apophis, Ra’s rival. Right after he does this, the soldiers return and the “gods” enter, looking for who is going to be the “Children of the Gods”. Making their rounds, Daniel tries to sacrifice himself to be close to Sha’re in some form. 
But instead, Skaara is chosen. As they leave, Apophis says “Kill the rest.” 
The leader replies, “Many have said that…but you are the first I have believed can do it.” He turns and fires on his own men. Jack grabs a staff weapon and blows a hole in the wall. The prisoners escape out the hole, and Jack convinces the leader to come with him.
Jack asks him his name, and he find out his name is Teal’c. 
They and the prisoners arrive at the gate at the same time as Apophis and the other Goa’uld. The ship drops them off, then proceeds to strafe the escaping prisoners.
The situation is extremely dire, until SG-2 pops up with a rocket launcher and shoots it down.
He knocks Jack back with a Goa’uld hand device and then proceeds through the gate. 
Jack is visibly crushed, but there is no time to be concerned about that. They are almost out of time. They are surrounded by Jaffa, who are closing fast.
On Earth, General Hammond finally gives the order to seal the gate and lock out their transmitters. Back on Chulak, Daniel finally dials the gate.
As soon as Hammond hears that, he retracts his last order. 
On the gate pedestal, they trip and in that moment, a larval Goa’uld burrows in the back of his neck. 
He shakes it off, not quite realizing what happened. They jump through the gate and the gate is locked down behind them. Everyone is happy to be home and leaves the gate room after a minute or so. Kawalsky stays behind for a minute longer…and his eyes glow. 
While they're sitting there, a tarp falls off the Stargate and someone starts dialing in. As the wormhole opens, they draw their weapons. One female Airman moves up close to the gate, curious. She's grabbed, and a firefight ensues. 
The Airmen take out a few of the assailants, but in the end are no match for them. One manages to sound the alarm and the base goes into lock down. By the time the strike team gets to the gate room, the gate's already been dialed and the remaining attackers leave, taking the female Airman with them.
Back at the base, General Hammond, the new general in charge of Cheyenne Mountain, talks to Jack, questioning him about the mission and asks him if he had indeed detonated the nuke on Abydos. When he answers that he did, Hammond reveals that they are going to send another nuke through. Jack is forced to admit that while his team did detonate the weapon, they detonated it aboard Ra's ship and they faked that gate on the other side had been buried.
In addition to Kawalsky and Ferretti, Captain Samantha Carter, an astrophysicist, also joins the team. 
When they leave, they're told that they have 24 hours to return or send a message.
They had run hundreds of other addresses through the computers without finding another address. But according to Daniel, they didn't have a critical component. He takes them to a room with a ton of writing on the walls. It turns out that map of a huge Stargate network. 
Sam initially says that it couldn't be possible, until Daniel suggests that the gates could've drifted apart. She realized that would account for the addresses not working, and says that, using the map as a basis, she could set up an equation that could account for the shift. While staring around the room at the huge amount of addresses, she remarks "The aliens could've come from anywhere..."
They take Sha're and Skaara and leave just before Jack and the rest of the team show up. 
When Jack and the team go back to Earth, they bring Daniel with him. Before he leaves, he tells Kasuf to bury the gate for 1 year after they leave. 
If, on that day, he didn't return an check in, they were to rebury the gate forever, cutting themselves off from the Stargate network. After the emotional good-bye, SG-1 steps through the gate. 
Stargate
travels, SG-1 has not found anyone with technology that surpasses the Ancients in every facet. At their civilization's height, they were unmatched in science, technology and military might. While some civilizations have come close to their level of advancement (The Asgard), no one has yet surpassed them. In fact, due to the fact that the Ancients ascended to another plane of existence, no one even knows the full extent of their capabilities and research.
that possesses a human host to survive. The resulting combination is an exceptionally strong creature with enhanced strength and extreme longevity (when paired with their resurrection device, the Sarcophagus). They use this and their advanced technology to set themselves up as gods. Taking humans from Earth thousands of years ago, they spread them throughout the galaxy and began to rule over them as various gods from human mythology. Notable Goa'uld System Lords include Apophis, Anubis, Hathor, and Sokar.
The Jaffa are the slaves of the Goa'uld. They are descendants of humans that have been modified to that they have to serve as an living incubator for larval Goa'uld. Without a larval Goa'uld, the Jaffa will die soon after hitting puberty due to a failing immune system. In fact, if the symbiote is removed from an adult Jaffa, they will die a slow, painful death within a matter of hours. They must either acquire a new symbiote, or they require regular injections of a drug developed by the Tok'ra, called tretonin. The Jaffa often where armor with a helmet resembling the a specific animal. For instance, all of Apophis' Jaffa wore helmets resembling serpents.
The Replicators are mechanical beings composed of nanotechnology. Their main goal is to increase their numbers and spread across the universe by assimilating the advanced technology of other species. For this reason, the Replicators are opposed to all other life-forms. They started out as an arachnid-type androids, but in "Unnatural Selection", they developed human-form Replicators. Normal Replicators are resistant to energy weapons, like the Jaffa staff weapon, but can be broken apart and destroyed by projectile weapons. However, human Replicators are resistant to both types of weapons because they're make up of smaller blocks that resemble cells. They were eventually completely destroyed by the Dakara Superweapon in Season 8.
The Ori are a group of Ascending beings who are incredibly similar to the Ancients. They use their ascended powers and infinite knowledge of the universe to force other lesser beings to worship them. The Ori differ from the Ancients in one key way, their life view. The Ancients value science while the Ori value religion. They created a fake religion known as "Origin" to sway beings to worshipping them. Origin is designed to channel the energy created by the human worshippers to the Ori. So, while they promise Ascension to their followers, they won't acually help other Ascend because they would have to share the energy they sap.