The episode starts when Finn finishes building Flame Princess' new house, which Flame Princess loves. A small fire spreads to Finn's feet, which he says doesn't hurt as much as it used to, but the fire accidentally spreads to the rest of his leg and he screams, then runs in a panic towards a nearby lake. Flame Princess and Jake then rush to the side of the cliff and look at the water to see if Finn is alright. After doing some tricks that Flame Princess and Jake think are funny, Jake pulls him back up on land. Flame Princess thanks Finn for building her new home. Finn and Flame Princess try to hug, but they're interrupted by Jake, who knows that Finn would be burned by her. Jake wraps Finn in tin foil and when he is finished, Finn and Flame Princess hug. They let go after a while, and then Finn and Jake walk away into the forest, saying goodbye to her.
Finn didn't know if the hug was okay and asks Jake for tips. Jake's advice is to "let things take their natural path" and he explains some "junk" about dating. He creates "tiers" or a set of stairs with his arm and then explains that Finn is "at Tier 1, which is hugging, but pretty soon, you'll be at Tier 2, which is smoochin'." Jake then explains about tiers 5 and 8, using references that would apply only to Lady Rainicorn, such as "touching her horn for the very first time." When Finn points out Tier 15, Jake tells him to "stay away from that." He then tells Finn that he needs a shower because he smells. The two enter the treehouse, to see Princess Bubblegum has broken in to collect taxes. Finn then tells Princess Bubblegum to "not inhale" while he goes up a ladder to take a shower. Jake then reveals in an outburst to Princess Bubblegum that he's hanging out with Flame Princess. Princess Bubblegum is distraught from this, and quickly runs-off, forgetting the taxes. Jake is confused, but is interupted by a video chat with President Porpoise. The next day, as Finn is going to leave to hang-out with Flame Princess, he is stopped when Princess Bubblegum is standing in the doorway, causing Finn to shriek in surprise. She then attempts to explain to the duo why Finn can't see Flame Princess, but in the process, Finn leaves and Jake falls asleep. Princess Bubblegum then thinks that Jake understands what she said, but he wasn't listening to Princess Bubblegum and then thinks that she's really jealous of Finn and Flame Princess.
Later, Finn returns from his date with Flame Princess, not accomplishing Tier 2. Finn asks what Princess Bubblegum was talking about and Jake tells him that she's jealous of Finn and Flame Princess, which makes Finn frown. Jake then tells Finn that the best way to get to Tier 2 is with a "sappy poem". So he helps Finn write one, but as Finn is explaining his feelings toward Flame Princess and how she makes him feel, Jake falls asleep again. Finn is seen later at a hill at sunrise trying to gain inspiration for the poem, which succeeds when the sun comes up, then Princess Bubblegum shows up and asks if Jake explained why he can't see Flame Princess anymore. Finn retaliates by saying that he loved her, but she didn't love him back. He assumes that Princess Bubblegum is trying to get him to fall in love with her again, to which he claims that he's ready to move on and that he won't let her ruin everything, so Finn leaves, a clearly confused Princess Bubblegum picks up one of the scraps of paper Finn wrote on and quietly exclaims "Oh, no!". Jake is seen later making and singing Bacon Pancakes, when Princess Bubblegum appears again and asks Jake if Finn is with Flame Princess, and Jake says that that's his "man's biz". When she continues to pry at the subject, Jake retaliates by yelling at her. Princess Bubblegum explains that Flame Princess's elemental matrix can't handle extreme romance, and that if Finn kisses her, Flame Princess will burn through the Earth's crust and core, destroying it from the inside. Princess Bubblegum then says that's why she had the Flame King lock her up inside the lamp, to contain her.
The two rush over to Flame Princess's new home, where Finn is reciting his poem to Flame Princess, but midway through, it gets burned to ashes, which causes the two to laugh, and afterward, kiss. Flame Princess then burns very brightly, explodes, and starts burning a hole through the Earth's crust. Finn (who appears to have been injured due to the kiss because his lips and parts of his face are burned) grabs one of Jake's arms, ties it around himself, and jumps into the hole after Flame Princess. Jakes struggles with the weight and falls on the hole, sealing it. Princess Bubblegum says that if Jake is depriving Flame Princess of oxygen for 24.8 seconds, she will burn out, which will stop the process. Finn reaches Flame Princess and sees that she has passed out and turned a very light shade of blue. Finn (struggling to breathe) says that he needs her "to be okay." He kisses her and gives her air, which awakens, rekindles, and stablizes her, though it causes Finn to pass out from the lack of air. Jake pulls the two up. Finn (who appears to be even more burned) awakens and asks Flame Princess if she is okay. Finn then kisses a rock, and holds it out to Flame Princess who also kisses the rock to symbolize them "kissing." The two walk off, and as this happens Princess Bubblegum sighs sadly and whispers "Oh, Finn." She turns around and sees Jake staring at her with a grin and he says "Jeeealous?", to which she replies, "Shut up."
- Flame King (Mentioned)
- Lady Rainicorn (Indirectly mentioned and drawn)
- Tree Trunks (Cameo)
- President Porpoise (On video chat)
- This episode had over 3.5 million viewers, currently making it the highest rated episode of the series.
- When Jake explains the tiers to Finn, he's talking about his and Lady Rainicorn's relationship.
- Princess Bubblegum says she told Flame King to lock up Flame Princess because she was physically unstable and could destroy the world from the inside, this could explain why Flame Princess was locked up all this time and could also explain why her father says she is "evil" referring to a physically unstable girl.
- The Promo art shows Princess Bubblegum with a crying Flame Princess who is locked up.
- Finn kisses Flame Princess three times, the last kiss being an indirect one through a rock.
- When Jake was drawing in the mud at the beginning of the episode, he was drawing Lady Rainicorn.
- When Princess Bubblegum is explaining to Jake why Finn cannot see Flame Princess, her holo-screen contains:
- y = mx + b ± c which is the formula for a line on a Cartesian coordinate plane, except the "± c" is superfluous.
- A picture of the Earth with the giant crater.
- Finn and Jake pay taxes to the Candy Kingdom, even though they live in the Grass Lands.
- Flame Princess' quote, "Do the thing that I like!" hints that Finn and Flame Princess have been going on dates since Incendium/Hot to the Touch.
- The foil Jake uses to wrap Finn before hugging Flame Princess is called "Foiled Again."
- The box Jake is using to cook from holds enough pancake mix for a 200 ft tower of pancakes.
- Princess Bubblegum diary entries include:
- FINN + LOVE + FLAME PRINCESS.
- A formula containing the Chinese character for romantic love, 愛, and ∞ the symbol for infinite
- A formula containing the information "AUG," "18," and "y=2012."
- In this episode, the snail is in the top from the door of Princess Bubblegum's room.
- The title card is a reversal of the title card for "Incendium." Finn is crying with photos of Princess Bubblegum in Incendium, while it is reversed in Burning Low with Princess Bubblegum crying with photos of Finn.
- Jake acknowledges how much Princess Bubblegum hurt Finn back in "Incendium."
- This is the second time Flame Princess burned out. The first time was "Incendium."
- The music that was played on BMO was used in a title card for "My Two Favorite People".
- This is the second time The Morrow has appeared, the first was "Death in Bloom".
- This is the second time the fate of the world has been at stake, with the first being in "Mortal Folly."
- Flame Princess continues the running gag of royalty or people of high standing leaving their homes.
- This episode puts the fate of the Marauders in question as Flame Princess' new home is in the exact same spot that the Marauders' village used to be, insinuating her house is made of debris from the destroyed village. Finn throws a Maurader helmet into the fire as the finishing touch for Flame Princess' new home.
- In this episode, the way Finn and Flame Princess kissed looks different on how characters used to kiss. For example, like how Finn kissed 13 year-old Princess Bubblegum in "Too Young."
- When Jake is cooking, the front right burner of the stove is on, but when he turns around to talk to Princess Bubblegum, the front left burner is on.
- When Finn is outside at sunrise, if you look closely, you can see a dot above a giant cloud on the right.
- When Finn and Flame Princess were trapped in the hole, and Jake was blocking it with his body, PB's jewel on her crown was purple, not blue.
- The first time you see the "Pancake Tower" box, tower is displayed as "Touer."
- When Jake is explaining the tiers to Finn, the difference in steps between tier 8 and tier 15, which is the end of Jake's hand, is only 2 steps and not 7.