If you missed last week's Chuck, check out a recap here.
"Chuck vs. Operation Awesome" picks up right where the previous episode ended, with Captain Awesome (hereafter called by his first name, Devon) captured by The Ring. Devon is being held on the roof of the hospital by Sydney Prince (Angie Harmon), operative for The Ring: Los Angeles. Sydney believes Devon to be a world-class CIA spy, and she needs him for something. Back in Castle, Chuck is freaking out about Devon's safety. Casey and Sarah tell him to relax and just go to work. They can't do anything for Devon until he is contacted by Sydney again -- if she thinks he is a spy and he doesn't do what she says, she will kill him. Chuck tries to talk himself into being calm, but is unsuccessful.
Morgan, too, is unsuccessful in keeping his emotions in check. Despite Big Mike's love of his mornings alone (it is a time for reflection and pastry after all), he has called Morgan into his office to discuss Morgan's future with the Buy More. Big Mike has noticed Morgan getting more respect from his co-workers, so he asks Morgan if he, "Son," would like to be Assistant Manager. Morgan, although still weirded out by his mother's relationship with Big Mike, accepts. An agitated Chuck, meanwhile, is working the floor at the Buy More. He dismisses a Japanese customer, and when she has some choice words for him, Chuck flashes Japanese fluency and tells her off. Now further discombobulated, Jeff and Lester ask Chuck to settle an argument: who would win in a fight, Jean-Claude Van Damme or Steven Seagal? To illustrate his query, Lester playfully karate chops at Chuck. Well, the Intersect doesn't discern between a real or pretend threat, especially when Chuck is not in control of his emotions. Chuck's kung fu skills kick in, and with one roundhouse kick to the face ("Boom Boom Pow!" yells an impressed Jeff), Chuck lays out Lester. Devon rushes in, to Chuck and Sarah's relief, and tells them that he's scared, "They think I'm a spy, Chuck. They think I'm you."
Back in Castle, Casey, for one, thinks The Ring has made a completely believable mistake, "One of them looks like a spy, the other looks like Chuck." Over Chuck's protestations, General Beckman says that they need to use Devon to infiltrate The Ring. When Chuck and Devon arrive home, Devon tries to explain to Ellie where he has been. He runs through an utterly ridiculous story about how he was running in the park when he saw a cat in a tree, but the cat was a bear and he had to wrestle it and finally decapitate it. Ellie is incredulous. Chuck jumps in to save his brother-in-law and explains that, actually, Casey was completely drunk in the park. He was so drunk that he was arrested after exposing himself, so Devon went down to the station to talk a cop friend into dropping the charges. Ellie believes them, and when Casey walks by, is thoroughly creeped out.
Later, Chuck, Sarah and Casey are planning "Operation Awesome." Chuck is told that he needs to be Devon's handler for the mission. Chuck remembers what it is like to not know how to be a spy, so he is best equipped to help Devon. Devon knocks on Casey's door and tells the team he has received a package from Sydney. When she calls, she instructs Devon to put on the earpiece and watch that are in the box. Upon doing so, the earpiece latches on to Devon's ear. Sydney informs him that the earpiece is rigged with explosives: try to take it off or not follow her instructions, and she will detonate it. Very not awesome. Devon is to go downtown to the Crystal Towers building and await further instruction. Chuck gives Devon a second watch to be used to communicate with the team. Chuck has helpfully labelled the two watches "Good Guys" and "Bad Guys" so Devon won't get confused. The "good guys" go down to Crystal Towers and put Devon into play. He has been told to go up to the 12th floor. Chuck decides that he has to help Devon get there safely and tells Devon to wait for him in the building's lobby. There, Julius the security guard inquires into Devon's purpose in being at the building so late at night. Devon explains he's there to see his friend Chuck. Julius asks why Devon is so nervous, Devon tells him he just can't take all the lying anymore. It's too much pressure on him and it's not fair to his wife. Julius is sympathetic, "If you really love this Chuck, you have to tell your wife. You can't live a lie. Trust me. I've been there." Chuck ends this embarrassing situation for Devon by shooting Julius with a tranquilizer gun and hustling Devon up to the 12th floor.
The would-be spies arrive upstairs and are met by men on either end of the floor. As the men pull their guns, Chuck flashes sharpshooting skills, pushes Devon out of the way, and masterfully takes out the men with tranq darts. Devon asks if Chuck learned how to shoot like that from the CIA. Nope, it was years playing Duck Hunt (which is great, but no Wild Gunman. Just ask Marty.) Sydney tells Devon to get into the room at the end of the hall by cutting out one of the guard's eyes to open the retina scan lock. Devon, as a doctor, will not cut out someone's eye, so he and Chuck decide to just prop a guard up into the scanner. They enter and find they are in a CIA office. Sydney tells Devon to find and kill the agent inside. At that moment, Chuck loses contact with Sarah and Casey, who themselves are locked down in their van. The General confirms that they are indeed on lockdown. The mission is a set-up. Chuck and Devon are on their own. They find the CIA agent: he's special agent Daniel Shaw, or to most, Superman! Shaw had appeared briefly (and just as a hand with a lighter) at the end of "Chuck vs. the Three Words" when the General had pleaded with him to tell Chuck, Sarah and Casey of whatever plan he was hatching. That plan was now coming to fruition. Shaw knows exactly who Devon and Chuck are. He knows Sydney is coming to confirm Devon is joining The Ring so Chuck needs to kill Shaw. He takes a pill, hands Chuck a note to be read after Sydney leaves, gives Chuck a gun and points it at his shoulder. When Chuck protests that he hates guns, Shaw says he hates guns too, before shooting himself. Chuck hears Sydney's heels click-clacking down the hallway so he hides himself and gives Devon the gun. Sydney checks Devon's alleged handiwork, welcomes him to The Ring, and leaves. After she's gone, Chuck reads the note which says Shaw took amiodarone (a drug used for irregular heartbeats, and which stopped Shaw's heart), and that there is a medical kit to save him in the desk. Dr. Devon jumps into action, and reminiscent of Pulp Fiction, plunges a needle into Shaw's chest, reviving him.

I don't know if agree with your statement about Shaw. I believe he is a 'love interest' of sorts for Sarah. It seems like they had some sort of history. Perhaps he wife isn't dead, but was Sarah and now they are divorced? Just my thoughts, but I felt like that's where the writers were leading us to believe.