O'Neill suddenly finds himself a little disoriented on Thor's ship. He begins to hear a strange sound and moments later is faced with hundreds of menacing looking metallic bugs. He freezes as they swarm past him. O'Neill heads in the direction the bugs came from and comes upon a very weak Thor. Thor tells O'Neill that he is dying and directs him to a control panel for further information as he is too weak. O'Neill learns that these bugs, called Replicators, are artificial organisms that have overtaken the ship and have directed it to Earth. The effects of the Replicators reaching Earth would be devastating. 

O'Neill appears back in the briefing room of the SGC in the form of a hologram and informs General Hammond and the rest of his team of the situation. He orders them to gather a large amount of explosives that he will transport up. The team, of course, wants to be transported up as well, but O'Neill orders them not to come. 

O'Neill can't believe his eyes when the explosives arrive with SG-1 in tow. They have little time to formulate a plan to outwit the Replicators and destroy the ship before it reaches Earth, hopefully finding a way to save themselves in the process. ~ Sci-Fi.com official episode synopsis

Paul: "General, I wish it wasn't always under such... unusual circumstances. Any further word on the situation?"

General Hammond: "No. We've been unable to make radio contact with SG-1."

Paul: "Well, it's possible the Asgard cloaking device is also blocking radio signals."

General Hammond: "I see you've done your homework, Major."

Paul: "General, all I do all day long is read up on the Stargate Program."

General Hammond: "And then?"

Paul: "We hit it with everything we've got."

Daniel: "Uh, SG-1 is on that ship."

Paul: "I have as much confidence in SG-1 as you, Dr. Jackson, but they left over an hour ago. We've had no communication since, and we have no idea what kind of a time frame we're dealing with here."

General Hammond: "Let's give them a reasonable chance, Major."

Paul: "Yes, sir. I'll try to define reasonable to the Pentagon."

Daniel: "They've disabled the ship's cloaking device."

Anonymous Airman: "Object's on a controlled entry."

Walter: "Projected landing on the West coast of the United States, sir."

Paul: "Of course, this could also be a sign that they've already lost the battle."

General Hammond: "This is General Hammond. At this time, I recommend going to Def Con 2. Deploy all available assets to intercept the alien ship."

Daniel: "General."

General Hammond: "I'm sorry, Dr. Jackson, but if that ship makes it through the atmosphere intact, we have no choice but to assume SG-1 failed. We must destroy it but whatever means necessary."

General Hammond: "The Joint Chiefs will respond."

Paul: "I'll have to call you back!"

Daniel: "They're gonna use it to escape!"

Paul: "Like you did from the Apophis mothership! It could work!"

Daniel: "It will work! The--the--they'll gate to another planet, then home."

General Hammond: "You had a DHD.  They don't."

Paul: "Even disconnected, there should be enough power to dial out once."

Walter: "The target has changed heading. It's dropped out of controlled entry vector. Target is breaking up."

Paul: "We have visual confirmation. A fireball headed for the Pacific Ocean, 400 miles off the coast of California. Naval recovery teams are moving in to deal with any wreckage. I'm sure you were right, Dr. Jackson. The point of commandeering the stargate had to be an escape."

Daniel: "I just hope they made it out in time."