In this game our main mission is to stop the Collectors( aliens who are kidnapping entire human colonies.) Collectors are working for a sentient race of machines the Reapers( Reapers destroy all advanced civilizations every fifty thousand years.) In the beginning of this game Collectors attacked and destroyed our ship Normandy. Our main character Shepard died in the process of the attack. Secret pro human organisation Cerberus and their leader Illusive Man somehow brought us back to life and build as a second Normandy. Now we are gathering the team of most badass scientists, soldiers and mercenaries to save galaxy and humanity from Collectors and the Reapers.
In the last part we recruited a last companion, a Geth named Legion and did his loyalty mission. After that collectors attacked our ship Normandy and abducted the normal people from our crew. So at the moment we only have a pilot Joker and main combatants of the team.
In this part we very angry that Collectors took our crew so we used Omega 4 Relay and launched a suicide mission to travel to collector station and wipe them out once and for all. After that Jack came to our room. She finally accepted that she loves us and let her guard wall down. So we enjoyed a moment together before heading to face the Collectors. Then we spoke with Illusive Man. He wished us good lack in our final battle.
After we passed the Omega 4 Relay Collectors sent their troops to stop us. They managed to get to our cargo chamber. But there we found and destroyed them. Then Collectors sent a a giant ship that in the past destroyed our first Normandy and killed us. But this time we were prepared for a fight- our ship was upgraded so we were able to tank enemy attack and and blast their ship to hell. After that we crash landed on Collector base. Then we assigned jobs to our team. Somebody had to go thru tunnels and open doors for us. We also separated to our crew to a dew different teams and trusted our boss Garrus to lead the second team. Later we found the colonists and our kidnaped part of the crew. Colonists were melted into liquid and absorbed. But we managed to save our non-combatant part of the crew just in time. Then we asked Jack to hold a biotic field and protect us from collectors swarms. We sent Mordin back to the Normandy with the people of our crew who we saved. After that we found out that collectors were building Human-reaper by melting colonists bodies. We defeated this abomination and were preparing to blow collectors base. But then Illusive Man called us and asked to give him reaper technology instead of destroying it. He claimed that this would lead to advancement and supremacy of humanity. We told Illusive Man to shut up and not to interfere. We set the station to blow up. After that we barely managed to escape but our entire team survived the ,,suicide mission.''
After escaping the blast we once again had a talk with Illusive Man. He complained that we destroyed the station. But we were done listening to his orders and decided to finally be our own boss. After that Joker gave us some info on the Reapers. They are coming and there are many of them. After that we spoke with our crew one final time. Grunt and Garrus expressed that even reapers(godlike giant machines) should fear our might. And Thane said that he was glad that he joined us before his death. Thus ended the base game of Mass Effect 2 but we still have to do one DLC before we start Mass Effect 3.