How does Nicholas become the acting chief of cardiac surgery?

When Alistair wakes up, he demands to see Nicholas. Alistair is in pain, but he is still his own self when he tells Nicholas to take care of his patients but not to mess with his desk. Nicholas goes to Alistair's office and is sitting behind the desk when Elliot Saget, the chief of surgery, walks in. Saget tells Nicholas to get used to the office because he will be acting chief while Alistair is away for the next six months. Nicholas finally has everything he wanted, but he has no one to tell.