Mass Effect 2 introduces a vast array of specialists, and Commander Shepard needs the help of every expert they can convince to ally with them against the Collectors. To scientifically understand more about the enemy and how to defeat them, the Illusive Man provides Shepard with a dossier for a Salarian biological weapons expert, Mordin Solus.
According to the dossier, Solus is operating a medical clinic on Omega, where they also must travel to recruit Archangel. Currently treating a virus running rampant through various species who inhabit Omega's slums, finding and recruiting the professor will take a lot of convincing and effort, but the work is worth the reward of his valuable expertise and addition to the team.
Mission: Arrive on Omega
Upon docking on Omega, EDI will inform Shepard about the plague ravaging the slums and advise them to speak to Aria T'Loak at Afterlife. It is not essential to speak to Aria before heading straight to the slums, but she can provide Shepard with essential information. The first opportunity to earn Paragon/Renegade points presents itself outside Afterlife, where a couple of Batarian thugs are causing problems. After dealing with the Batarians, head inside and ask to speak with Aria; while questioning her, ask about the Salarian scientist.
Once finished speaking with Aria, head to the quarantine zone, where a Turian is guarding the entryway and arguing with a human about getting inside. +5 Paragon points can be gained by telling the Turian to let Shepard in so they can help, or +5 Renegade points will be gained through intimidation by stating, "I'm going in." +2 morality points are offered here if Garrus or Grunt are in the party, as well; Paragon by telling them they can stay behind and Renegade by telling them they are needed despite the danger to their well-being. If Shepard did not deal the outside guard using morality and a fight broke out, expect to be fired on by the other guards upon entering the quarantine zone.
Bypassing the inside security, go straight and pick up the refined eezo crate. Turn back around and head toward, then around barrier, picking up the Medi-gel on the way to the door. Get through an encounter with the Blue Suns and then head across to the hackable terminal for 5000 credits. Bypass the lock to enter the room and find four audio logs detailing the grim deaths of a couple of Blue Suns mercs from the plague, and pick up the powers cells before going back out.
Follow the path to the suffering Batarian on the ground, gaining +5 Paragon points for offering to ease his suffering with some Medi-gel and another +2 by saying, "I'm here to help," or +2 Renegade for saying, "I need information" or ignoring the morality interrupt and letting him die during his coughing fit. If he survives, he has a lot of information about the Professor, his clinic and his unorthodox methods and skill with weapons. Someone can be sent back to help him from Mordin's clinic after arrival.
Bypass the door and head down to find another Batarian, this one dead. Listen to the audio log he left and hack his wall safe for 4000 credits. Return to the upper level and turn right, heading into a few encounters with the Blue Suns that can be fought either on the first or second level. There is a medi-gel pack and spare parts worth 1000 credits on the first floor, so be sure to go back for them if fighting on the second level. After the enemies are cleared, cross the plaza and bypass the doorway on the right to find two human refugees holing up inside. While speaking to the refugees, there's an opportunity for morality points when trying to convince them to leave the apartment: +5 Paragon for offering to help them or +5 Renegade for telling them hiding won't save them. Before leaving, retrieve 4000 credits from the wall safe and the medi-gel pack on the table.
Coming back out on the other side of the plaza, scan the dead merc for the assault rifle upgrade before proceeding into the next fight, which features both the Blue Suns and the Blood Pack mercs battling each other. This will not stop them from turning on Shepard when entering into the fight. The Vorcha will not advance but fire from a distance, and the pyros will send out shooting bursts of flame while the Krogan and Varren charge into an up-close and personal battle.
After disposing of all the mercs, head into the next apartment at the top of the stairs on the left. There is a container of eezo in there, as well as two looters who've been taking advantage of the chaos in the plague zone. The opportunity for morality points arises when letting them know looters aren't appreciated. Either choose to reason with them for +5 Paragon or opt to shoot them for them +5 Renegade. Heading back down the stairs, follow the signs leading to the clinic.
Mission: Mordin's Clinic
Arriving at Mordin's clinic, the guards outside note that any trouble will invoke the wrath of the mechs and Professor Mordin Solus himself. Entering the clinic, take time to speak to everyone interactive to learn more about Mordin and the work he's been doing. Head down the hallway and into the room on the left-hand side to find two crates with palladium and platinum, a medi-gel pack and a computer terminal with research to increase medi-gel capacity. Mordin is in the next room, but before speaking with him, pick up the items in the room, which include two resource crates with eezo and iridium, medi-gel and a power cells crate.
Speak with Mordin and try to keep up. He's a fast talker and he has a lot to say. There is an opportunity for a Paragon/Renegade interrupt that will grant +5 points for the option chosen. Mordin tells Shepard he's developed a cure for the plague, but he needs someone to distribute it. Shepard can gain an additional +2 Paragon for easily agreeing to take care of it, or +2 Renegade for asking why nothing is ever easy. You'll have a few more dialogue options with Mordin, including telling him to send someone for the sick Batarian, and then he hands over a new heavy pistol, the M-6 Carnifex Handcannon. He will also ask Shepard to keep an eye out for his assistant, Daniel, though that is not required to complete the recruitment mission.
Mission: Environmental Controls
Leaving the clinic, head up the stairs and into the next fight with the Blood Pack. Take them out, and then find the gambling terminal, which can be hacked for 3000 credits. There is also a medical station to retrieve a medi-gel. Moving forward and toward the next flight of stairs, there is a staircase leading upward. Hack the nearby terminal for 5000 credits, then go up the stairs where there are two doors. The door on the right continues the main mission, while the door on the left holds a few angry Batarians and Mordin's missing assistant. Talking to the Batarians is an opportunity to gain some Paragon points, while killing them will grant Shepard Renegade points.
Take the other door and fight through hordes of Blood Pack mercs until heading down a set of stairs leading to the Environmental Control Room. Fight through the waves and head down the stairs when they've been cleared to enter the control room. Upon entering, a Vorcha announces that they are in league with the Collectors, and the next rounds of battle commence. Vorcha fire from the inaccessible upper levels, while Krogan join in from the stairwells leading down to ventilation controls. Take out the enemies on the first floor before heading left and down the first set of stairs, where more enemies will advance between the party and the control room. Dispatch them and head inside the first ventilation control room to turn on the first fan.
Head back up, across the room and down the other side, battling through enemies along the way to reach the second ventilation control room to turn on the other fan. Once both fans have been activated and Mordin's mission has been completed, Shepard will automatically return to the clinic.
Mordin Solus, Recruited
Returning to Mordin's clinic, he will thank Shepard if they saved his assistant and note that plague levels are already dropping. Ready to join the squad in their fight against the Collectors, he will note that Cerberus working with aliens is unexpected. Shepard can either leave the mission immediately and head back to the Normandy or remain a few moments to ensure everything was picked up at the clinic before departing.
Back on the Normandy, Jacob explains what they know about the Collectors. Mordin notes that all he needs is a laboratory, at which point EDI chimes in, directing him toward the lab facility that will become his base of operations for the remainder of the game. Inside the Research Lab is the Upgrades station, where any upgrades offered by squadmates or found in the field can be implemented.