Two weeks after the Carboniferous Period mission, the time has come to rescue the park's very first Permian period target...the mighty dimetrodon! Meanwhile, at the same time that Drew is in the Permian Period with the Denhams, Leon spends his medically mandated time 'on break' from active rescue duties working to improve his skills as a keeper. And in the process, he proceeds to overcome his natural nervousness around invertebrates while at the same time developing a particularly close bond with assistant veterinarian Yolanda Hall.
- Accidental Passenger: A combined group of acleistorhinus, captorhinus, kahneria, and rothianiscus end up getting brought to the future for display at the titular park completely by accident when, at a time in which the rescue team happen to have their backpacks lying around unzipped on the ground, the animals in question crawl inside in curiosity to see if there's anything inside that they can eat, only for the rescue team to reclaim their bags and zip them closed while the animals are still inside. From there, the animals end up trapped inside the backpacks until the rescue team return home to the safety of the park, at which point they end up in ideal position to join the other rescued contemporary animals from their home period amongst the park's repertoire.
- Adaptational Personality Change: In Prehistoric Earth, the dimetrodon behaved similarly to cats and tegu lizards. Here, their behaviors have more in common with those of alligators.
- Agony of the Feet: Leon's ankle has recovered from its nasty bite injury given by Sasha just enough for him to still work as a keeper at the park so long as he's careful. But its still enough to guarantee that he sits out on the rescue mission this time. Yolanda herself also ends up bitten on the ankle by Sasha not too long after she accidentally falls into the crassigyrinus pool, but miraculously manages to avoid getting injured as badly as Leon had been.
- Always a Bigger Fish: Rommel the dimetrodon proves to be this for no less than seven sphenacodon when they make an admirable, but ultimately failed, attempt at stopping him from stealing an edaphosaurus carcass (that, for bonus points, they themselves had initially been at odds over). Similarly, Andrias the proterogyrinus proves to be this for the crassigyrinus when he's released into their pool to frighten and scatter them long enough for Leon and Yolanda to escape from them.
- Amphibian Assault: The eryops and acheloma prove unnervingly willing to try to attack the rescue team after making their introduction. And even after their rescue, one of the eryops very nearly manages to bite an arm off of one of the holding pens keepers. The slaugenhopia rescued beforehand are likewise eager to go hunting the diplocaulus that are living in the same lake as them. And back at the park, Yolanda is very nearly mauled by the crassigyrinus, which are themselves scared off by Andrias the proterogyrinus long enough for Leon to escape their pool with Yolanda.
- Amphibian at Large: The eryops and acheloma are fairly large prehistoric amphibians that get rescued during this mission. The proterogyrinus and crassigyrinus from the previous mission also play a prominent role in the 'back at the park' subplot.
- An Arm and a Leg: One of the eryops (possibly Grime) very nearly bites an arm off one of the holding pens team keepers over the course of their efforts at herding it through the holding pens.
- Animal Stampede: Played for laughs in the case of the combined herd of casea and cotylorhynchus that get startled into running straight towards the rescue team and through the portal by a small pack of ophiacodon that don't even manage to make it all that close to the herd before the herbivores make it through the portal. Played straight, however, with the edaphosaurus herd that end up spooked into stampeding by an elderly sphenacodon on the hunt. And much like with many similar stampedes in past episodes, this herd has a single elderly male at the very back of the herd that fails to make it through the portal alongside the rest of the herd in time before ending up killed. And at the very end of the mission prior to the final back at the park scenes, a massive combined group of various animals end up stampeding through the portal after being scared into going through by an avalanche.
- Attack! Attack... Retreat! Retreat!: The sphenacodon that get rescued are initially perfectly happy to try to fight against Rommel the dimetrodon in order to prevent him from stealing the freshly killed edaphosaurus that they were initially on the verge of fighting each other for when Rommel arrived. Unfortunately, all it takes is a single loud bellow from Rommel, plus him starting to charge right towards the sphenacodon immediately after that, for the sphenacodon to all decide to cut their losses and let the dimetrodon take the kill.
- Big Creepy-Crawlies: Amongst the animals rescued are meganeuropsis (a dragonfly species even bigger than meganeura) and the winged walking stick-like insect known as titanodictya.
- Big Damn Heroes: The rescue team, naturally, prove to be this for several animals that would have otherwise been killed in an avalanche near the end of the mission, as well as to several herbivores getting hunted by carnivores. Leon himself also proves this towards Yolanda when she ends up accidentally falling into the crassigyrinus pool (albeit, with help from Andrias the proterogyrinus).
- Crash-Into Hello: Leon and Yolanda's first proper meeting and session of interacting together begins with the two of them accidentally colliding with each other while they're both on the way to the Carboniferous Dome.
- Damsel in Distress: Yolanda ends up needing to be rescued by Leon (with assistance from Andrias the proterogyrinus as well as the rest of the staff in the area) after she is accidentally knocked into the crassigyrinus pool.
- Dreadful Dragonfly: Much like with the meganeura in the previous mission, this is averted with the even bigger meganeuropsis featured in this episode (to the point that they're not even as hard to rescue in comparison).
- Enemy Mine: Fafnir the elderly sphenacodon and an entire small group of younger fully grown adults are initially in competition over who gets to eat an elderly male edaphosaurus that Fafnir has successfully killed for himself. They immediately decide to team up when Rommel the dimetrodon arrives to try to steal the kill himself. Ultimately, this is not enough to stop Rommel from successfully claiming the carcass for himself. And at the very end of the mission, a massive group of multiple different animals are all mutually afraid of an avalanche that is triggered into heading their way by a lightning strike.
- Enemy Summoner: A rare non video game example in that not too long after Grime the eryops lunges out of the lake he's first in at the time of his introduction, he lets out a low bellow that soon turns out to be a signal for three other eryops, plus a float of acheloma to rise out of the same lake and join him in an advance towards the rescue team.
- Face Your Fears: Leon works to overcome his nerves around invertebrates for the sake of improving his keeper skills.
- Fantastic Fauna Counterpart: Lampshaded by Jack when he takes note of how an elderly sphenacodon killed an edaphosaurus in a hunting style similar to that used by modern day komodo dragons. Likewise, the dimetrodon, eryops, and acheloma behave similarly to alligators and crocodiles over the course of their respective rescues.
- The Glomp: How Yolanda expresses her gratitude towards Leon for saving her.
- It's All My Fault: Matt is understandably apologetic over accidentally knocking Yolanda into the crassigyrinus pit via his careless handling of his clipboard.
- Kindly Vet: Yolanda, as per usual. Bethany also proves this (though not without a small degree of firmness to her personality as well).
- Loud of War: As per usual, the use of airhorns proves a valuable strategy in attracting the attention of several animals that get rescued.
- Malicious Monitor Lizard: While not truly monitor lizards (or even in the same scientific family), the sphenacodon are shown to behave very similarly to komodo dragons.
- Meet Cute: A possible interpretation behind the Crash-Into Hello between Leon and Yolanda. And the way they behave not too long after they've both gotten back on their feet certainly adds weight to this interpretation.
- Moment Killer: Adrian and Kaisumi by virtue of giving a meaningful 'ahem' and giggling (respectively) at the sight of Yolanda hugging Leon in gratitude for him saving her life and Leon seeming quite happy about as much.
- Mythology Gag: Leon's scenes during the back at the park segments are heavily based upon similar adventures he underwent in The First Steps back in Prehistoric Earth.
- Named After Somebody Famous: The very first dimetrodon rescued is named Rommel (after famed WWII German general Erwin Rommel).
- Never Smile at a Crocodile: The eryops and acheloma display some very crocodile-like behaviors over the course of their rescue, with a large male eryops named Grime proving particularly vicious over the course of his rescue. Rommel the dimetrodon also displays several alligator-like behaviors in his introductory scene. The crassigyrinus also once again act fairly similar to crocodiles in their attempts at attacking Yolanda. And so does Andrias the proterogyrinus in his work at scaring them off.
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Reality Subtext: When the combined herd of casea and cotylorhynchus end up proving themselves unexpectedly easy to rescue by almost immediately charging straight over towards the rescue team not too long after a small pack of ophiacodon has only just started trying to circle menacingly around them, Drew states (admittedly while smiling), "Well that's surprisingly easy - I'm almost disappointed that there isn't more of a challenge," before summoning the portal in time for the herbivores to come charging right through to the present. One look at the retrospective for Prehistoric Earth will show how this comment of character!Drew's is heavily based upon a far less good natured comment from writer!Drew involving his thoughts about how that story ultimately turned out. - Red Eyes, Take Warning: Rommel and the other dimetrodon all have blood red eyes.
- Religious and Mythological Theme Naming: The elderly male sphenacodon rescued alongside a small pack of younger fully grown adults is named Fafnir. One of the male pulmonoscorpius rescued in the previous mission is also revealed to have been named Scorpio.
- Rescue Romance: Leon's rescue of Yolanda in this 'episode' is heavily implied to be the start of their romance from Prehistoric Earth being reprised in this story.
- Scary Scorpions: Leon still proves fairly unnerved by the pulmonoscorpius. In fact, he deliberately works to overcome this obstacle by directly working to feed them for the sake of improving his skills as a keeper.
- Scary Teeth: When Rommel is first introduced, there is one moment in which especially heavy emphasis is placed on his visibly sharp fangs (with some of them even being explicitly broken).
- Sea of Sand: Averted. Despite there being elements of a desert environment, the Permian Period landscape the rescue team travel to for the sake of rescuing the dimetrodon also comes with elements of forest environments, rivers and lakes, and even hills and mountains with the tops covered in snow.
- Shark Pool: The crassigyrinus enclosure ends up unwittingly fulfilling the spirit of this trope when Yolanda is accidentally knocked in.
- Ship Tease: A heavy dosage of this is provided in this chapter for Leon and Yolanda.
- Shout-Out: The Amphibia themed names for animals continue via a diplocaulus named Wally and an Eryops named Grime. And the chapter's name is itself borrowed from the title of a Jim Thompson novel.
- Shown Their Work: As Drew points out when he, Jack, and Alice take note of their being snow present in the Permian Period desert landscape, the Permian Period occurred when the Earth was in the midst of an ice age. As a result, snow is actually not as out of place as most media would have you believe.
- Spiders Are Scary: As much as he's attempting to overcome his nervous tendencies around invertebrates, Leon is still very noticeably unnerved at the possibility of working with the megalorachne to the point that he eagerly chooses to save them for last over the course of his efforts at working with the Carboniferous period invertebrates.
- Summon Bigger Fish: Right as it looks as if the crassigyrinus will successfully overwhelm Leon and Yolanda despite the former's admirable efforts at keeping them at bay, Andrias the proterogyrinus is released into the crassigyrinus pool by Adrian; at which point the noticeably bigger carnivorous amphibian is able to startle and frighten the smaller amphibians away just long enough for Leon to swim over towards the subsequently dropped escape rope with Yolanda in his clutches.
- Surprisingly Realistic Outcome: As determined as Leon is to save Yolanda and despite him putting up a decent fight with only a metal rod to defend himself and Yolanda with, that still doesn't change the fact that he's going up against eight 2-meter long carnivorous amphibians largely by himself (since Yolanda is at this point both unarmed and not even fully conscious) directly within the waters of their habitat in which they'd quite likely have a Home Field Advantage. And in the end, it's only thanks to Andrias the proterogyinus being released right into their pool at the exact moment that they're seemingly on the verge of finally overwhelming Leon and Yolanda that the latter two manage to successfully escape via emergency rope dropped their way by the other staff in the Carboniferous Dome.
- Take That, Critics!: As described under Reality Subtext, Drew's 'almost disappointed there wasn't more of a challenge' line can be interpreted as a lighthearted jab against original Prehistoric Earth creator and cowriter Luczynski's needlessly harsh and meanspirited slamming of the aforementioned fanfic in said fanfic's 4th anniversary retrospective.
- Teeth-Clenched Teamwork: Very much still the case between Kyle and Nikolai.
- Threatening Shark: Averted with the shiver of small and relatively harmless freshwater sharks known as xenacanthus.
- Took a Level in Badass: Leon manages to both work to overcome his nerves at handling the scorpions and proactively dive into the crassigyrinus pool to rescue Yolanda when she accidentally falls in (albeit, with a little help from Andrias the proterogyrinus).
- Unwitting Instigator of Doom: In his enthusiasm at Leon joining in to help him, Adrian, and the other researchers present with their attempt at doing further research on the meganeura, Matt accidentally lets go of his clipboard while thrusting the hand that's holding it skyward. As a result, the clipboard goes flying into the air and lands very close to where Yolanda is standing, startling her into walking backwards towards the railing of the bridge she's on, at which point she steps on a wet area and slipping over the rail...straight into the crassigyrinus pool located directly beneath the bridge.
