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 helped Miranda save her sister from her father. We also stopped a fight between Miranda and Jack.
In this part we met with our old friend Liara. During the years we we had not seen her she became an information broker. She told us how we can find our next companions- assassin Thane and justicar Samara. We decided to look for Thane first. To do that we had to go speak Seryna. She told us that Thane is trying to kill asari named Nassana. We knew Nassana from the first game there she asked us to kill her sister. So she was not a really nice person and so Thane trying to kill her was not a big surprise. Seryna took us to Dantius Towers where Nassana was hiding.
While climbing the towers we had to fight many Eclipse mercenaries and mechs. We also saved multiple salarian workers who were locked up for their safety by the assassin. We found an Eclipse Trooper who pretended to be a badass and was not willing to answer our questions. So we pushed him from a window of the tower. Finally we found Nassana and her last remaining guards. Nassana believed that we are the ones who were hired to kill her. So she made us a generous offer to spare her life. But while we were talking with her Thane snook in and killed last guards and Nassana. He did it all in a blink of an eye. After that we talked to Thane and he agreed to join us on our mission to stop the Collectors. Also Thane told us that he is dying.
Once we returned to the Normandy Jacob said that he doesn't trust Thane because he is an assassin. We told Jacob to shut up and reminded him that we are in charge. Mordin expressed delight for working with us because for him our curent mission seemed simpler and not a morally problematic as modifying genophage. After that we spoke with Jack and asked why she is distancing herself from us. It turns out that in the past she had a boyfriend who sacrificed his life to save her. We told her that we can't fix that but we will be staying with her anyway. After that we talked with Thane and asked him more about his deadly illness.He told us that scientists are trying to create a cure but he is unlikely to live long enough to see this treatment come to fruition. After that Miranda was jealous that we became new favorite agent of Illusive Man.