If Laudanol works by removing fear, why does Chuck stop strangling the Ring’s goon when Sarah calls to him? Is it some other emotion (like love) or is it because she is his superior officer and handler?
It’s because of Sarah and his love for her. It’s her voice and her presence that bring him back and cancel the effect of the Laudanol. When Chuck turns towards Sarah, the Laudanol is still in full effect. It’s when he recognizes her that the effect wears off.
The Laudanol plot is there to show Chuck and confirm for Sarah that it’s not the lack of feelings that makes the perfect spy (as Chuck said at the beginning of the episode, “No feelings? I could work perfectly“). Yes, he could work perfectly, as we can see during the fight, but at the cost of becoming a terminator and the ruthless spy (killing machine) that the government has in mind, not the human being and the spy that Chuck is and wants to be after his turnaround at the end of 3.08 Fake Name. But Chuck’s and Sarah’s feelings for each other erase the effects of the feeling-removing Laudanol. What makes Chuck perfect is precisely the fact that he has feelings.
Some raise the objection that the point of any drug is that one can’t “think” his way out of its effect. A drug that can be counteracted by an emotion is not really a drug. The only way for that scene to make sense for these viewers is that Chuck stands down when a superior officer demands it.
The problem with this interpretation is that it clashes with the whole purpose of the episode, which is about feelings, not orders and chains of command. It also clashes with what we see on screen—Chuck clearly stands down when he recognizes Sarah for who she is, and that realization is what immediately undoes the effect of the drug, which clearly wears off immediately, restoring Chuck to his normal state. He doesn’t stand down because of orders. He clearly stands down because Sarah brings Chuck back, and he realizes what he’s doing. It’s not about orders. It’s about feelings.
The main point of season 3 is to analyze and resolve the issue of feelings as a liability or as an asset in the spy world. The issue of feelings as a liability was introduced and accepted by Chuck and Sarah in 2.03 Break-Up (for Sarah) and again in 3.02 Three Words (for Chuck). It was the whole reason Chuck and Sarah couldn’t be together, but it’s rejected for Sarah in 2.18 Broken Heart, when Beckman admits that Sarah’s feelings for the asset are, well, an asset and not a liability, and it’s finally rejected for Chuck here in 3.10 Tic Tac, as it must since Chuck and Sarah are about to finally get together for good, and in order to get together, they must reject the conclusion that feelings are a liability for spies.
Notice the exchange at the beginning of the episode. Chuck perks up when Beckman talks about the effects of the Laudanol. He says that, without emotions, he could work perfectly. Sarah turns to him and says, “yes, but then you wouldn’t feel anything” and has a concerned look on her face.
The Laudanol here is the episode’s Chekhov’s Gun. It’s introduced early in the episode with the exchange above and will “go off” when Chuck takes the pill. Notice he’s about to kill the Ring goon the same exact way that Casey just killed Keller, and Sarah witnesses both events, thus confirming her earlier fear that Chuck on Laudanol would become a terminator spy like Casey (or all other spies). Notice Chuck’s reaction. He turns towards Sarah with Laudanol killer instincts in his eyes, then he “sees” Sarah, and the drug’s effects immediately wear off and he looks at his hands with incredulity at what he was about to do, and finally realizing that his earlier hope of working perfectly without emotions is not what he wants.
What we are supposed to get here is that feelings are not a liability in Chuck’s spy world. They are an asset. Feelings are what makes Chuck human and what makes it worth being a spy. It’s not worth being a spy if you dehumanize yourself.
In this context, it’s perfectly fine for the drug’s effects to immediately wear off when Chuck “sees” Sarah because love makes us human and thus defeats the effects of a dehumanizing drug. We could think of Laudanol as a drug that inhibits the subject’s emotions and of Sarah as the trigger that releases the neurotransmitters of emotions in Chuck’s brain that counter the effect of the drug.