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.
Also, not to be confused with a Door Stopper.
- 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.
- Mahou Sensei Negima!: 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.
- Nimoy!Spock in the new Star Trek.
- The mirror entrance to Dracula's castle in Van Helsing.
- In Serenity River does this on purpose to protect the rest of the crew. The door mysteriously unjams at the end, however...
- Although it was only jammed from the one side in the first place.
- Harry Potter:
- 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.
- 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.
- 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...
- The Star Trek TOS episode "Arena", where aliens force Kirk to duel the lizard creature alone on the planet's surface. This is a case where the hero being stranded was actually the plan.
- Variations on this occur a number of times, notably in "The Savage Curtain" and "Spectre of the Gun".
- Also in TOS, 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.
- In the Doctor Who episode "Dalek", Rose is not quite fast enough to make it through the security doors and ends up trapped with the Dalek.
- In the episode "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 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.
- 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 in the demon world and managed to escape because all the demons were fighting over who should get to go through.
- 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.
- Done with Ramza in Final Fantasy Tactics, for one-on-one battles. The entire party is isolated in the end as well.
- 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.
- Cortez set his ships on fire after landing in Mexico, thereby making the conquest of Aztec empire somewhat of an only way to go.