Marshall gets his heart checked after the death of his father -- and so did Ted, Lily and Robin. Everyone but Barney does it. Robin announces she's thinking about getting a dog again. Marshall says she really needs a man because now everyone is with someone, including Barney "with" Nora. Barney says he's not "with Nora," but he is on, under and behind her. Lily teases him about having feelings for Nora, and Barney announces his "one rule" (he has several of these): Never go out with a girl more than once. When Lily asks him why he's going out with Nora again, he announces the exception to the rule (the same exception to all the other "one" rules): Unless she's hot, which is why nothing is going to stand in the way of tonight being "legen -- wait for it..." and Barney sneezes.
He shows up to see Nora and is sneezing, coughing, sniffling and hacking. Nora takes Barney home and takes care of him, feeding him, helping him use a Neti pot, and playing the violin while he sleeps.
Robin brings home a young guy named Scooby. Marshall mocks her for bringing home the first guy she bumped into on the street.
Barney pulls Lily aside and tells her he made an appointment with the cardiologist and he wants her to go with him because he's "a lot scared." She agrees, but on the condition that he won't lie to Nora. The doctor tells him his heart is fine, but he might have a slight arrhythmia, so he has to wear a heart monitor for 24 hours. The doctor asks him what happened at 8:46 p.m., because she noticed some irregularities. He remembers he was at dinner with Nora and she told him she wants to get married -- not necessarily to him or immediately -- and she hopes it doesn't scare him off. He remembers recalling Lily's mandate that he not lie to Nora, and then he remembers he told Nora, "That's exactly what I want to."
Back in the doctor's office, Lily slaps him.
Back to the night before, Scooby talks about chasing squirrels out of his backyard, then he runs to the kitchen after smelling food. Marshall says he's a dog. Not that he acts like a dog, but that he actually is a dog. They remember him chasing his tail, sticking his head out of the car window and catching frisbees with his teeth.
When he comes back, the gang asks Scooby how they met. They use a bunch of dog puns in their questioning, then he says he's from Labrador in Canada, and Lily can't believe this is happening.
Barney shows up with Nora and they recall their conversation about the married life with children they're envisioning. Robin says it's unbelievable. When Nora gets up to use the restroom, Lily punches Barney in the chest, and the doctor says that would explain his 14-second cardiac arrest. Back to the previous night, Barney insists he's not lying to Nora. He says she's "really special, in fact, I think I'm falling in love with her." He gets even more emphatic that he's serious, then threatens to pull out the most embarrassing thing about each of them if they don't assure Nora that Barney is a nice guy. For Lily, it was her classroom's pet turtle. For Marshall, it was "calzone." For Robin, it was the "Mr. T dream." And for Ted, after a couple of tries with "ballet class" and "NSYNC concert," the most embarrassing thing was, "Thermos." They all agreed to cooperate.
Nora comes back and Marshall says Barney is the kind of guy you'd bring home to meet your parents. She says her parents are in town and asks him if he'd like to meet them. This is a big deal, because Barney has only one rule: Never meet a girl's parents.
Barney and Nora leave and Robin asks Ted to hang out with Scooby because he doesn't know anyone in the city. Ted is annoyed because he knew that if Robin got a dog, he'd end up taking care of it all the time. Then Scooby says he was at the park and bought a big bag of "sandwiches" (it's marijuana, but Old Ted's altering the details for his kids who are hearing the story). Lily says, "We're in our 30s, we don't smoke sandwiches." When "sandwich brownies" are proposed, she's in.
We next see Ted and Marshall in the apartment talking about how hungry "sandwiches" make them, and Ted asks Marshall to explain the "calzone" story to him. Marshall says Barney once saw him drop a calzone on the sidewalk, pick it up and keep eating it. Ted tells him not to worry because the calzone sounds amazing. Lily brings an empty pan from the kitchen and they all realize they don't know where Scooby is. The door is open and they think Scooby got out.
Barney is walking Nora home and she invites him inside. He accepts, but then admits that he doesn't really want to get married and he's been lying all night because he wants to get in her pants. She slaps him. At the doctor's office, Lily slaps him. Then he turns to the doctor, who also slaps him.
The gang calls Robin to tell her Scooby got out. She says she's on her way home and Ted asks her to pick up some calzones.
Barney apologizes to Nora, but says it's her fault because she shouldn't have just told him exactly what she wants out of the relationship right off the bat. She leaves.
Robin, Lily, Marshall and Ted are eating calzones on the street as they wander around looking for Scooby. Barney shows up and they ask if he's seen him. Barney notices Scooby across the street taking a leak on a fire hydrant, and Scooby turns and runs back toward them and we hear car tires screech and horns honk.
"That explains 12:51 a.m.," the doctor says. She says there's nothing wrong with Barney and he should live a long and happy life, as long as nobody stabs him. Lily says Barney is lying to himself, and he was lying to Nora about lying to her.
Lily asks Barney what time his dinner reservation was with Nora. He says 8:30, so she asks the doctor what Barney's heart did at 8:30. She looks and they realize that when Nora walked into the restaurant and he saw her, his heart literally skipped a beat. Lily tells him his heart is telling him something and dares him to listen to it.
We next see Barney go to a place where Nora is having a meal with her parents. He walks in and says that when he said he lied, he was lying. He admits this is totally new to him. He's confused, but he wants to be confused with her. She stand up, smiling, and introduces him to her parents. But after this scene plays out, we see Barney just imagined it. Instead of going inside the restaurant, he looked down and walked away.