...With the Blackwood group with him, they watch as it reveals the truth: after the scientific team sent on their research mission (never mind the fact that early episodes made evident that the events of '53 was an invasion effort) are killed, Malzor, whose mate was on the exedition, kills their leader, and makes every effort to wage a war against humanity as an act of revenge. (This gives way to the fact that this is the first and only invasion made by the Morthren, so one can't help but note the confliction of this with the subtitle for the season). In doing so, he has caused the planet to be set for self-destruction. This is then shown to Mana who shows it to the Morthren just as Malzor is ready to launch an all-out massacre. After a cornered Malzor kills Ceeto, Debi shoots Mazlor dead. With this, the Morthren call off the war, and our heroes walk out into a suddenly sunny world.

The first season's finale, "The Angel of Death", introduces a synth from the planet Qar'To (which is in the same system as Mor-Tax) named Q'Tara who arrives on Earth and begins killing aliens right and left in effort of finding the Advocacy, without whom the aliens would be lost and helpless. The Blackwood Team is happy to have such a powerful ally (who can shoot "atomic bullets" and can easily detect aliens) on their side who seems to be fighting the same enemy. In fact, after the aliens launch a surprise attack on them all, Q'Tara even goes the extra mile to heal the fatally wounded team members. Although she has been doing good so far, she needs to bring in reinforcements. Just as she's prepared to leave, she makes a last report in a strange native language (subtitled), which states that her mission is incomplete and that humanity as a future food source is still in danger.

This set-up in this cliffhanger combined with the existence of the rogue alien Quinn vying for his own global dominance and millions of more aliens with their leaders making the exodus to Earth in such a short strand of years made the future of the show promise nothing but interest with so many friends and foes battling for the planet. Sadly, all this potential died in the aptly titled Season 1 finale, as they were never picked up and carried into the second season.

Another element that was being built was the issue of why no one remembers the invasion of '53 (something that is the centre of the show's criticism). Many hints of the true explanation were dropped in many episodes, but this was something that Season 2 never even acknowledged, much less answered.

FROM : WIKIPEDIA