When the hero is isolated from most of his allies and other outside help and forced to confront a villain or some other dangerous situation alone.
Perhaps the hero has just gone through the portal when it suddenly breaks, leaving him with no way back. Perhaps everyone is fleeing but the hero, probably because he is More Hero than Thou, insisted on everyone else going ahead of him and thus didn't make it in time. Either way, he's trapped with the big boss or in some other dangerous situation, and there's no way for anyone else to come help.
Usually this is caused by a Phlebotinum Breakdown at the worst possible moment, but occasionally the situation in question could be designed to only let one person through. The plot does not usually revolve around finding a way back; it's usually a simple excuse to isolate the hero with the villain or monster.
Compare Point of No Return, a specifically video game variant.
- Dragon Ball Z has a heroic version in the Buu Saga. Piccolo convinces Super Buu to fight Gotenks in the Room of Spirit and Time (AKA Hyperbolic Time Chamber) so that, if Buu proves to be too powerful, he can simply destroy the door and trap the three of them in the room forever. Unfortunately, Buu is so powerful that he actually rips a hole in the fabric of space-time by shouting and escapes. Thankfully Gotenks is powerful enough to do the same after he transforms into Super Saiyan 3, but Piccolo reams him out because his sandbagging and showboating got them into that mess in the first place.
- Negima! Magister Negi Magi: Negi's party gets trapped in the Magical World when the Portals are destroyed by Fate and Cosmo Entelechia.
- A lot of the outworlders in The Keys Stand Alone: The Soft World are apparently victims of this, which is how they got to C'hou in the first place. Different people talk about spells sending them into a rift, or hitting a teleport trap, or simply being sent to the wrong place when their ship warped, and finding themselves trapped on C'hou.
- In Star Trek V: The Final Frontier, the transporter has just enough power to beam up Spock and McCoy, leaving Kirk stranded on the planet with the vengeful god.
- In The Matrix, Agent Smith shoots the phone just after Trinity gets out, leaving Neo with no exit and no choice but to fight him.
- In the first Terminator movie, Reese explains that the time machine got blown up just after he followed the Terminator through, so "It's just him and me." The subsequent movies also featured just two Terminators going back in time, so apparently he was misinformed. Or made subtle changes to the timeline that resulted in a slightly different future, just like what is stated to have happened to varying degrees in the next two movies.
- Han Solo riding out to save Luke in The Empire Strikes Back, even though he knows that he won't be able to get back before the doors close.
- In Serenity, River jumps into a horde of murderous Reavers, fights a few of them off, and jams the only door that would allow them to attack her allies. However, that leaves her to fight a small army alone.
- The Wild Geese. As the mercenaries are driving across a bridge an aircraft drops a napalm bomb on it, forcing the unit to split into two groups.
- Harry Potter:
- Harry Potter and the Philosopher's Stone has Harry and Hermione reach a wall of flame and only have one potion that will take them through the flames; thus, Harry has to confront Voldemort alone.
- Harry Potter and the Chamber of Secrets had this occur when an attempt to sabotage a rescue of Ginny Weasley caused a cave in to separate Harry and Ron, forcing Harry to proceed alone.
- In A Hat Full of Sky, young witch Tiffany Aching leads the Hiver (a sort of serial-possessing entity) through the portal into Death, only to discover the door has closed behind her. This presents her with the problem of opening it again...
- Downplayed in James and the Giant Peach: When James first enters the peach stone and finds himself face to face with the huge creatures, his first reaction is pure terror, and he considers running back through the door the way he has come, only to find that it has disappeared. However, the creatures then become his allies.
- Star Trek:
- In "Arena," aliens force Kirk to duel the lizard creature alone on the planet's surface and prevent the rest of his crew from assisting him. This is a case where the hero being stranded was actually the plan.
- In "The Savage Curtain," Yarnek disables the Enterprise's transporter until they show whether good or evil is stronger. This leaves Kirk and Spock stranded on an alien planet without the support of their crew, with only a pacifist alien and Abe Lincoln to aid them in fighting history's greatest villains.
- In "The Tholian Web" Kirk gets stranded in "interspace" with only limited air in his spacesuit, while complications ensue for the rest of the crew.
- Doctor Who:
- In "Dalek", Rose is not quite fast enough to make it through the security doors and ends up trapped with the Dalek.
- In "The Girl in the Fireplace", the Doctor broke through a time window to the eighteenth century, breaking the connection of all portals leading to his TARDIS but one which was disconnected at the time.
- In "Heaven Sent" the Twelfth Doctor is trapped in a Confession Dial, without his companions. He has to figure out how to escape, and relive events until he makes it out.
- In The Sarah Jane Adventures, when Sarah, Jo, the Shansheeth, and Colonel Karim are trapped in the room with the memory weave self-destructing and the doors deadlocked.
- In Goodnight, Sweetheart, Gary Sparrow has a personal time portal that normally allows him (and only him) to travel between present-day London and London during the Blitz. But in various episodes, the portal doesn't work or it works by different rules.
- Blake's 7. In "Gold", Avon stays back to Hold the Line against guards who've chased them into an airlock transfer tunnel between two spaceships. Unfortunately one ship is about to do a Hyperspeed Escape and so the tunnel seals automatically, stranding Avon on the wrong side — he's saved by a Teleportation Rescue while a poor Red Shirt is sucked out into space. A blooper has the door closing too slowly and Avon getting through, causing the cast and crew to break out laughing.
- Near the end of season 3 of The Mandalorian, Paz Vizla seals the door behind him to allow Bo-Katan to get Grogu and the rest of the Mandalorians to safety. He fights off a platoon of Stormtroopers clad in beskar-alloy armor, first by firing his gun until it overheats, then chucks it at a trooper to unbalance him so he falls over the edge with a push, and then continues fighting the rest in melee. He defeats them all with great difficulty, then three Praetorian Guards show up, defeat him, and he pulls himself up one's blade to try to choke him, Defiant to the End.
- HeroQuest: In the expansion "The Return of the Witch Lord", one of the quests ends with the characters being trapped in the central room with a gargoyle, the door disappearing when the last character enters. When the gargoyle is defeated, the characters are captured by the Witch Lord.
- Many traps in Doom and Doom II locks you up in a room with an army of monsters to kill, with the switch to open the door again being very well hidden, behind all those monsters, or non-existent (which forces you to search for a new path in order to find your way back). Notably is the 8th level of Doom II, Tricks and Traps, where you're thrown into a small room full of Baron of Hell and the strongest boss in the game, the Cyberdemon.
- Kingdom Hearts:
- In Kingdom Hearts, both the second fight against Riku and Ansem begin with them summoning a magical barrier cutting Sora off from his allies, Goofy and Donald. This justifies the Duel Boss between Sora and the game's most prominent villains.
- In Kingdom Hearts II, right after crossing the Point of No Return, the magical door Sora entered to face Xemnas closes, cutting Sora off from Mickey and Kairi and forcing him to make due with only his standard party members.
- Metroid Dread uses this trope much more frequently than earlier Metroid games; often, after the player finds the correct route to go, something will alter or change (such as a turnstyle moving, a floor breaking, or a hazard popping up) that prevents Samus from returning to a previous area until she's collected the necessary power-up to get past it. Atypically of a Metroidvania, this basically means that Samus is roughly able to explore the same amount of map after opening new areas. Even much later in the game, when Samus has collected most of her abilities, there are many spots that can't (or aren't supposed to) be reached until virtually the end of the game, after she has pretty much everything.
- This happens towards the end of Quake IV - Matthew Kane is the only person able to go through the Strogg teleporter to face the final boss, as he has been partially "Stroggified" himself and the teleporter is fatal to humans (as one unlucky soldier discovered the hard way). His squad mates are still able to communicate with him, though.
- Used in an unusual variant in Tower of God, where the Ragtag Bunch of Misfits were taken out onto the sea to go inside of a giant beast. After the administrators left them out on the open sea, they soon noticed that the motor didn't work anymore. It was rigged by the administrators. They were supposed to die out there or when they would meet Urek Mazino.
- Avatar: The Last Airbender: In "Lake Laogai", the protagonist and his Anti-Hero ally rush after an escaping villain with the rest of The Team not far behind. The villain summons a wall of earth to block the entrance and brainwashes the Anti-Hero, forcing Aang to fight both the villain and his own ally alone.
- There was an episode of Jackie Chan Adventures where a portal between the demon and human worlds could specifically only let one being through. Jade was trapped alone in the demon world and managed to escape because all the demons were fighting over who should get to go through.
- Cortez set his ships on fire after landing in Mexico, thereby making the conquest of Aztec empire somewhat of an only way to go.