The Enterprise comes across a small, futuristic pod adrift in space. Bringing the pod onboard, the crew inspect the pod and find what is apparently a human body, charred beyond recognition. The pod is more spacious that it appears to be, and a "black box" device was recovered from the pod. During the investigations, the Suliban shows up, claim ownership of the pod, and demand Archer to hand the pod over to them. Archer refuses, and the Suliban attempt to take the pod by force. The Enterprise manage to fend them off.
The Tholians show up too and also demand the pod. They retreat when Archer threatened to destroy the pod. Archer decides to rendezvous with a Vulcan ship which would bring the pod back to Earth for further study. Meanwhile, Trip determines that the "black box" is some kind of an emergency beacon. On the way to the Vulcan ship, the Suliban attack the Enterprise. The Enterprise arrive at the rendezvous, only to find that the Tholians had disabled the Vulcan ship. The Tholians and Suliban attack each other and Enterprise is caught in the crossfire.
The appearance of the Tholians could indicate that the Tholians, too, are another player in the Temporal Cold War.
A mysterious probe arrives at Earth and attacks the planet, devastating areas in Florida and the Caribbean Sea before it was destroyed. Over 7 million people were killed. The Enterprise is immediately recalled back to Earth. En route, the Enterprise was intercepted by the Suliban, and Archer was taken aboard the Suliban ship, where he meets the Future Guy. The Future Guy explains that the attack on Earth was carried out by a race called the Xindi, and the Xindi probe was only a test weapon, with the Xindi intending to destroy Earth using an even larger device in another subsequent attack. The Xindi had apparently received information that Humans will destroy the Xindi race in 400 years, and the attack was a pre-emptive strike. Such information was never supposed to be revealed, but was apparently conveyed to the Xindi by an unauthorised source. The Future Guy then says that he was giving Archer this information because the destruction of Earth will contaminate timeline.
The Vulcans advise against entering the Delphic Expanse, which is said to have strange and unexplainable properties, and where sometimes even the laws of physics do not apply. A Vulcan crew which entered the Expanse supposedly went insane, while a crew of Klingons once emerged from the Expanse with their bodies turned inside-out, but still alive.
It is unknown whether the Xindi attack was the result of somebody altering the course of history, or that history had recorded the Xindi attack of 2153, meaning that the attack was meant to have happened. Archer's analysis of the probe wreckage seem to indicate that the probe came from the future, suggesting some sort of future intervention. If the Xindi attack was indeed recorded in history, and since the other series of TOS, TNG, DS9 and VOY are all set in the future of this ENT timeline, then the 7 million deaths in this episode would fortunately have had no impact on the stories in the other series, just as the way it should be.
The Future Guy provides Archer with information about the Xindi, and says that Earth's destruction will contaminte timeline. Perhaps Earth continues to play a role in the Future Guy's plans and therefore must continue to exist, or the Future Guy has some ulterior motive in helping Archer.
