Earth's first meeting with the Xyrillians, whose damaged ship was hiding in Enterprise's warp wake, and which ended with engineer Trip Tucker carrying a Xyrillian embryo.
In the Enterprise episode Unexpected, a string of malfunctions leads the crew to a cloaked ship riding in their wake and drawing on their plasma exhaust. Its Xyrillian crew apologise and explain that their engines are failing, and Tucker spends three days aboard helping with repairs.
The alien environment disorients him, but he becomes friendly with the engineer Ah'len, who shows him a holographic chamber and a game played with a box of telepathic granules. Back on Enterprise, Phlox finds that the game has left Tucker pregnant. He is only a host and contributes no genetic material.
Enterprise tracks the Xyrillians down and finds them hiding behind a Klingon battle cruiser. Archer talks the Klingons out of destroying them, the Xyrillians hand over holographic technology in payment, and the embryo is moved to a new host.