“It Makes a Lovely Light” is episode twenty one of season one of Andromeda.
It’s Dylan’s birthday and Beka gives him an unusual present. Using the diary that Trance and Harper recovered in “Fear and Loathing in the Milk Way”, she has determined a slipstream path to Tarn-Vedra, the lost capital of the Systems Commonwealth, and apparently Dylan’s home planet (although it sounds like it was originally, and maybe still is, the home of another race, not humanity, the race which originally founded the Systems Commonwealth, even if, by all appearances, humanity became a dominant influence in it).
Tarn-Vedra is in the Andromeda Galaxy. Dylan referred to the Systems Commonwealth as having spanned three galaxies, but which three? And what are they counting as a galaxy? One is Andromeda, another is the Milk Way, but between the two are literally dozens of smaller galaxies (the exact number alters depending on the definition of a galaxy. The number is definitely way more than one, no matter what definition is used. Andromeda and the Milky Way may be by far the largest, but there are some significant others too).
For some reason, they decide to make the trip really fast, so Beka uses the drug Flash to give her a boost. With predictably unfortunate consequences.