After a couple of the best episodes yet, 'Chuck Versus the Tooth' is not very satisfying. The story is unconvincing in two key regards. Firstly, as Chuck begins having nightmares about an assassination plot, Beckman fails to believe him and sends him to a psychoanalyst, which ultimately leads to his institutionalisation. Given that he has the intersect, it's seems likely that he WOULD have flashes both when he's awake and when he's asleep, and that during sleep they would manifest as nightmares. In that case, his intel would be taken seriously, and if it proved false, he would be assigned a team of CIA specialists to examine the effects of the intersect on his brain, NOT a psychoanalyst, who encourages Chuck to talk about his father (incidentally, his father also seems like an ideal candidate to fix Chuck's intersect glitch, but no one mentions the possibility of tracking him down). It's also hard to believe that both Sarah and Casey end up despairing over Chuck instead of believing him.
Secondly, it's hard to believe that Ellie is so naive in this episode. When a creepy man pursues you from Africa, sneaks up on you in an electronics store and says "I'm actually here to see you. Can we go somewhere and talk for a bit? Somewhere private?" you say NO THANK YOU I WOULD NOT LIKE TO GO SOMEWHERE PRIVATE. When that man meets you on a park bench in the middle of the night, presents CIA credentials and tells you your father is in trouble AND he needs your help, but that you can't tell anyone about it, you go home and you TELL EVERYONE ABOUT IT. It's not plausible that Ellie would believe that this lone creepy stranger is a CIA agent, and happily accept that her brother's friend, neighbour and colleague John Casey is a bad guy. Nor is it plausible that a trained doctor would be so naive when it comes to meeting strange men in dark places and cooperating with them. All in all, this whole episode feels a bit like a nightmare, with Chuck - who was so happy in the last two episodes - suddenly schlepping around in a robe in a mental asylum, and Ellie unwittingly spoiling everything, handing over the secret location of her father to someone she meets in a darkened alley.
There are some redeeming feature of this episode. The adorable Anna makes a reappearance; Sarah and Casey's ultimate loyalty is heartwarming; there's a great comic scene in the asylum, when inmate "Merlin" and his friends suddenly remember their spy skills; and the storyline segues into a new and exciting direction for the season, in which Shaw re-emerges as Chuck's nemesis and all of Chuck's friends and family are inspired to pull together and save the day.