Uh, sorry for the wall of text. Got a little out of hand, especially when considering it covers less than 30 minutes gameplay but a lot happens there, so it had to be done this way. I don't expect anyone to actually read all that, it's just a bit of writing practice. 
Anyway, here we go:
Nathan Shepard's mood was still grumpy when he climbed the steps to the council chamber. He was still brooding about Udina's intervention earlier. It was not that he disliked Tali, no she even seemed capable enough. The problem was that it was not Udina's place to second guess him in military decisions, he was not his CO, Anderson was. But since the Captain had let the incident slide, there was not much to be done now.
The other issue that concerned Shepard was the upcoming meeting with the council. He did not suspect it would go too well. The evidence they had was solid enough for him but would the council be convinced by some audio recording that a quarian claimed to have salvaged from the corpse of a geth? After all, the quarians were not exactly in the best standing with the Citadel races and it might look very convenient, that one of them brought forward a reason for the council to intervene against their old enemy. Given the history of the two races, Tali's evidence might be dismissed for the simple fact that it was ultimately self serving. But there was nothing to it, they had to try and so Shepard stepped into the light of the Serpent Nebula's purple glow that illuminated the room through the giant overhead windows and faced once again the leadership of galactic society.
Two hours later, all of the Commander's previous concerns were forgotten - and replaced by a whole set of new ones. Shepard, the first human Spectre stood in the decon chamber of the Normandy's airlock, waiting to board. As he let the cleansing white beam of the decontamination array wash over him he tried to think back and make sense of all the changes the last 120 minutes had brought.
His initial fears about Tali's audio recording had been unfounded. Apparently the salarians had developed some sort of sound recognition software, that would analyze voices and relate them to people with the accuracy of a DNA scan. When it identified Saren as well as Matriarch Benezia and ruled the recording free of fraud or manipulation, the council was convinced. Apparently, that test had already happened by the time Shepard got to the council chambers so he arrived just in time to be pleasantly surprised by the news. It didn't take the council long to fall back into old patterns though. Despite the fact that they believed the humans' accusations against Saren, they were not willing to solve their own problem and apprehend him. Instead, they compromised and Shepard was made a Spectre, to give him the authority and the responsibility to hunt Saren down. But the joy over the achievement left the sour aftertaste, that was inherent to political scheming. On the surface, the council got to pretend that they took action against their former top agent, gone insane, the alliance got their man in the ranks of the Spectres and everybody was a winner. Well, at least everyone at the top of the food chain. The colonies in the traverse certainly didn't win. All they got was one guy, against an army of synthetics and Shepard himself wasn't sure if he should consider himself on the winning side either. Oh, he was thrilled to be part of the most elite special forces group in the galaxy and honored that he could perform this vital duty for the advancement of humanity but if it had been up to him as a person, he would rather have remained and advanced within the alliance military's chain of command. Now, his superiors were a bunch of politicians and despite the fact that officially he was above the law now, that could mean only one thing: More compromises. Shepard hated compromises.
Of course, he was not selfish enough to voice any of those opinions. None of these sentiments ever showed on Shepard's face during the ceremony. This was not his first barbeque and he knew how much was riding on this. So the outside world, the audience, and the cameras, they got to see the very best example of the human soldier, stern in expression but respectful in demeanor, concerned but confident, proud but humble in light of this historic occasion. Behind this facade however, Shepard's thoughts were already racing, trying to come up with a plan to find Saren and bring him to justice.
It turned out that Udina and Cpt. Anderson were way ahead of him in that regard. While he was chasing down leads throughout the Citadel, they had already planned for his eventual success and produced some initial points of interest to start his search for Saren in the Traverse. The most important news however, was that Anderson was stepping down and gave him command of the Normandy. Shepard didn't quite know how to feel about that, he had not known Anderson for long but he liked the man and it was clear that he was driven out of his well deserved position by political back room dealing. This was definitely not how Shepard wanted to gain his first command but in the end, practical issues had to take precedence here. Shepard was the only one who had the authority invested in him by the council to effectively chase down Saren and in order to do it, he needed a ship. He was honored to get the Normandy though. From the little he had seen of her, she was by far the most advanced ship he had ever stepped foot on, her crew seemed capable as well as professional and the new stealth system would be the edge, they would need against the overwhelming force, that Saren could rely on.
Suddenly the bright slow moving light of the decontamination system faded away and with a hissing sound, the inner doors of Normandy's airlock opened. When Shepard stepped onto the metal floor gratings of the bridge, he was greeted by the monotone voice of the ship's computer: "Logged: Commanding Officer is aboard."