Unnatural Selection

Plot:

The Asguard home galaxy has been over-run by the replicators, and they ask for SG-1's help. The Asguard believed they had trapped the replicators with a device that would slow down time, but it seems to have failed. They need SG-1 to enter replicator infested space, find the time dilation machine and reset it. When SG-1 land at the designated point, they meet 5 individuals, who control the replicators. The others reveal that they are an evolution of the replicators - composed of micro-cellular replicator blocks, and modeled on Reese, who created the original replicators. These others have reset the time machine so that time is moving more quickly within this area of space - to allow them to evolve and build an enormous army that can invade the rest of space. The minds of the team are probed by the first 4 others. However, the last member of the others (called Fifth) seems reluctant - he is described as weak by First, the leader of the replicators. He was an attempt to model Reese more fully, but the mistake will not be repeated. Carter senses his reluctance to probe her mind, but invites him to do so - and they agree a plan. Fifth will reset the time dilation machine to run slowly, and he will escape with the SG team. While time is passing slowly for his brethren, the Asguard will have hundreds of years to fix the mistake in the others. Fifth has to leave later than the SG team to avoid arousing the suspicion of the others; Jack orders Carter to set the timer on the device to activate earlier than Fifth has been told. SG-1 escape successfully as the time dilation device reverses the trend within the area of space, and makes time run much more slowly. However, Fifth is caught by his brethren, and realises that Carter had broken her promise not to leave without him. Carter and Jonas regret using Fifth's humanity against him, but even though Jack seems uncomfortable, he declares that Fifth wasn't human, and they made the only correct choice.