If you can't wait for the third season of ASHES TO ASHES, the sequel series to the worldwide hit LIFE ON MARS, to show up on DVD or come to BBCAmerica, this article from The Guardian newspaper will tell you in detail how it all ends in the final episode. It's a big spoiler, so think twice if you really want to know.
Personally, I thought this season was very weak story-wise, not nearly as compelling or as well plotted as previous seasons of either ASHES or LIFE. The show probably should have ended with a variation on this episode last season instead of limping pointlessly through seven more.
That said, the final episode tied up the two series in a way the felt right and packed an emotional punch, even if the "reveal" was obvious and strongly telegraphed from the start…and I mean going all the way back to LIFE ON MARS. It was certainly a much better final episode than the atrocious American take, which revealed that all the central characters were astronauts in suspended animation on a journey to Mars to conduct a "gene hunt." I kid you not.