Orphean Rescue

Everyone likes Susan. She's such a Nice Girl, on top of being Team Mom and Love Interest to Bob! But alas, tragedy has befallen her in the form of a very unusual "kidnapping", one where she's been removed (usually) against her will and taken some place beyond mortal ken and reckoning. It can be a physical kidnapping as she's dragged into The Underworld, or even a willing one if she's Ascended to A Higher Plane of Existence. Sometimes it's not the body that's gone but the mind or soul, which can happen if she suffers a Heroic BSOD and she's put into a Convenient Coma after getting lost in Cyberspace or a Dream Within a Dream. Maliciously, she may have been trapped in a Lotus Eater Machine or Psychological Torment Zone, or had her Soul taken into the Spirit World. Or she could be plain old dead.

Point is, she's gone in a very real sense from this physical plane, but in a way that doesn't preclude recovery.

So Bob and his allies decide to rescue Susan by going on an Orphean Rescue Mission. Much like Orpheus and his trip to the Underworld, the heroes will travel into a strange, otherworldy realm. It may be a Journey to The Center of The Mind, Susan's soul, a different era, another planet, a rabbit hole, the Spirit World, Purgatory, Limbo, Hell, the Underworld (again) or even Heaven (or a reasonable facsimile).

On their quest, they probably have to fight Threshold Guardians appropriate to Susan's subconscious/DarkAndTroubledPast (trust us, no matter how happy go lucky Susan [honestly] is, she's going to have at least some skeletons in her closet) or whoever/whatever is holding her captive. Freeing her may require that she help in the process, with a rather more literal use of an "I Know You're in There Somewhere" Fight, or helping her see the door in her Epiphanic Prison.

Once Susan wakes up, she probably won't remember anything, except as a vague distorted dream that leaves her with an urge to hug her friends and kick ass.

Anime And Manga

 * Black Rock Shooter: Mato becomes/fuses with the eponymous Black Rock Shooter and goes to the Otherworld to save Yomi from Dead Master.
 * The first two major arcs of Bleach both manage to be examples of this: First Rukia is taken to Soul Society (where, in spite of it being the afterlife, she is to be executed), then Orihime is kidnapped by the Arrancar and taken to Hueco Mundo.
 * Inuyasha: Early in the series, Kagome doesn't enter hell, but gets very close to the entrance to save a child's soul who had died.
 * Later on in the manga, Sesshoumaru takes the full trip To Hell and Back in order to save his Morality Pet Rin.
 * One of the many, many MANY subplots of Angel Sanctuary is about Setsuna trying to get back the soul of his beloved sister Sara. Cue travel to the Hades, learning she already left... and we have not even covered 25% of the series.
 * In Jack and The Witch the titular boy hero descends into a frigid cave full of growing and shifting ice to rescue the banished witch Allegra, who'd been sent there by the Harpy Queen to freeze to death. The Ice Cave and its subsequent shift into a magical battleground seem to be tied to the Queen's magic, as they fade out once her crystal ball is smashed.

Comic Books

 * During Mark Waid's run, the Fantastic Four rescued their fallen teammate Ben Grimm in this manner.
 * Sandman features at least two cases: The title character going into Hell to release an old love he'd condemned after she rejected him, and his son Orpheus's trope-naming trip to retrieve Eurydice.
 * A story arc of Secret Six had them doing this to rescue Scandal's lover Knockout.

Film

 * Inception had Cobb rescue Fischer and Saito from the deepest subconscious.
 * Funnily enough, Limbo's closest to
 * And, of course, Mal became  because Dom's attempt to rescue her from Limbo worked much too well.
 * Poltergeist: Carol Anne is kidnapped by the ghosts and taken to the astral plane where they are trapped.
 * The low-budget film Tequila Body Shots doesn't even hide the fact that the climax will be this: The protagonist's name is Johnny Orpheus. Plus...guess what he uses to bring his love interest back from where she is?
 * In What Dreams May Come, the protagonist goes into hell to find his wife's soul who is trapped in her own guilt after committing suicide.

Literature

 * Charlie and The Great Glass Elevator has Willy Wonka and Charlie go deep down to rescue Grandma Georgina from Minus Land, where she went after having reduced her age to below zero.
 * Overdrawn At the Memory Bank has this trope, though in this case, Apallonia knows exactly where Fingal's mind is; it's his body she's having trouble finding.
 * In Briar's Book, Briar follows his teacher into death to convince her to come back.
 * Full Tilt by Neil Schusterman involves a boy going to rescue his brother from some kind of hell, appearing as an Amusement Park of Doom, after he was lured in.
 * In A Wizard of Earthsea, Ged tries to save a dying child, following her soul on the way to the land of the dead; but he doesn't manage to keep her from entering it and being lost.
 * There's a medieval narrative poem, Sir Orfeo, loosely inspired by Orpheus, where King Orfeo successfully wins back his wife held captive by The Fair Folk. He plays his harp so beautifully that the king of the fairies promises him any reward he wants.
 * The Friendship Song by Nancy Springer has this with Harper and Rawnie venturing to the underworld to rescue the soul of a rock singer. It's then played with as he has to choose to come back on his own.

Live Action TV

 * Seamus Zelazny Harper did this a time or two on Andromeda for the AI of the ship. It included a combo Journey to The Center of The Mind that happened to be Cyberspace.
 * The Doctor Who two-parter "Silence in the Library" and "Forest of the Dead".
 * Most of the plot of The Lost Room is the lead character recovering his daughter from this situation.
 * The third season of the UK Being Human included one of these early on. It's not without larger consequences.

Religion and Mythology

 * Orpheus, duh. When Orpheus's wife died, he entered the underworld and convinced Hades to let her return to the world of the living. However, Hades allowed it on the condition that Orpheus lead his wife back without looking at her until they're on the other side. Unlike the majority of the examples on this page, though, he ultimately failed in his quest.
 * Similar to Orpheus is Izanagi, creator-god in Japanese Mythology. His wife Izanami died giving birth to the fire-god Kagutsuchi and fell to The Underworld, The Yomotsu. Izanagi traveled down the cavernous realm of the dead, only to be repulsed by his wife who is now an eternally decaying, maggot-ridden corpse. He fled the underworld as fast as he can while being chased by the local demons and Izanami throwing lightning at him. Eventually, he made it to the surface, and closed the way to the underworld with a huge boulder.
 * Similar to both of the above (this is an archetypal trope, after all) Ishtar's Descent Into The Underworld is one of the most well-known stories of Babylonian Mythology. In it, she descends into the underworld but angers its queen, Erseshkigal, and is trapped there. As the goddess of fertility, this is bad for the living, so Ea creates a servant and sends it to retrieve her, commanding Ereshkigal to let her go.
 * In the Heirs of Alexandria series,  assumes a Persephone like role to become Queen of the Underworld and use her powers to save everyone. Upset that she was tricked into this;   travels to the Underworld and Hades gives him a very Orphean-task. Return to the living world without looking back.   cheats by having one of their companions, a knight; walk in front of him on the way back, so he can

Tabletop RPG

 * Champions Organization Book 1 The Circle and M.E.T.E.: One of the adventure seeds for the Circle is having Oeramm attack the Circle, capture Aureole or a PC and take them back to his home plane, from which they will have to be rescued.
 * You can actually bring back dead people from The Underworld in Geist: The Sin Eaters, but not without paying some (very terrible) price to the Kerberoi.
 * While not going to the realm of the dead per se, some Changelings make it their mission to raid Arcadia to free the humans kidnapped by True Fae, themselves being victims of True Fae in the past. It's only more admirable when you consider just what kind of place Arcadia is, and what effect it has upon the fragile psyche of the Changelings.
 * Some werewolves also make it their mission to eject humans who are trapped in the Spirit World, although it's more having to do with keeping orders in their territories than altruism for the poor humans.

Video Games

 * This seems to be  of Drawn to Life.
 * Kingdom Hearts sets up about 7 or so of these in Birth By Sleep. Interesting because all 7 are important characters whose growth, contribution to the plot, and tragic downfall took up about the space of a full game each, and each of them went in a completely different way. So it's a bit of a task for The Hero to bring them all back, especially since he only has the barest hints that there is any saving that needs to be done.
 * Touhou 07: Perfect Cherry Blossom has the three main characters going to Hakugyokurou, a realm of virtuous dead (think Elysium), to take back the Spring essence of Gensokyo which is stolen by the hungry ghost Yuyuko.
 * In Touhou 12: Undefined Fantastic Object, it's the bad guys followers of Byakuren who seek to liberate her from imprisonment in Pandemonium.  The player characters mistakenly believe they're trying to resurrect a terrible monstrosity.
 * Fatal Frame 2: Mio shoots her way (with a camera!) through a village worth of hordes of vengeful ghosts to save her little sister Mayu. Bonus point for (in Best Ending route) going down into Abyss to retrieve her back. She didn't come out unscathed from the whole ordeal, but at least she's now closer to Mayu than ever.
 * Happens in some route in the Yuri Genre Visual Novel Aoi Shiro.
 * Deconstructed HARD in Persona 3: FES. The desire to bring back  cause the SEES to splinters and fights each other in Groundhog Day Loop.   Moral of the story: It's better to let go of deceased loved ones.
 * Note that the MC's initial persona is Orpheus.
 * However, this is basically the entire plot of Persona 4 in a nutshell.
 * And THAT MC's initial persona is Izanagi. Persona loves this trope doesn't it?
 * Gwendolyn rescues Oswald from the underworld in Odin Sphere.

Web Comics

 * Sinfest seemed to be going in this direction after Criminy started digging his way to hell in search of Fuchsia, but it led to a subversion.
 * Red vs. Blue has something like this for Church following Tex  at the end of Season 8 and into Season 9, followed by the rest of the squad trying to save him as well throughout the present timeline of Nine.

Western Animation

 * Teen Titans has Robin do this for Raven in the Season Four finale.
 * In Disney's Hercules,