Now Let Me Carry You

You take care of me, Simon. You've always taken care of me.

My turn.

—River, Serenity

Alice is always leaning on Bob for support. Whether it's because of poor physical health, mental instability or some other troubling factors, she's weak and dependent on Bob's kindness and care to get her by in life.

Then something happens to upset this arrangement: Bob winds up wounded, incapacitated or possibly cornered by an army of bloodthirsty zombies. He can't get out of this mess by himself. He's clearly toast.

That is, unless Alice has anything to say about it. Which she does.

Whether it's because of Character Development or a hidden Chekhov's Skill that never proved to be much of an asset until now, Alice gets her chance to take the active role in the relationship and stand up for the one who has so long stood up for her, protect the person who protected her, take care of her caretaker. The helped becomes the helper.

The reversal in roles can be emphasized with dialogue (such as the Trope Namer Stock Phrase -- "You carried me, now let me carry you") or by making the moment visually a clear parallel of earlier scenes, only with the parts switched around.

This trope very frequently results in a Crowning Moment of Heartwarming. Sometimes it also serves as a Crowning Moment of Awesome for Alice.

Examples of Now Let Me Carry You include:

Anime & Manga

Konoka to Setsuna in the cinima town chapter of the Kyoto arc of Mahou Sensei Negima. Setsuna had always carried Konoka bridal style while protecting her. Having just unlocked her hidden healing abilities to save Setsuna's life, Konoka held Setsuna in the same manner to fully illustrate the reversal of roles.
Baam was practically raised by Rachel and he grew so dependent on her that he followed her in to the titular Tower of God as she abandoned him. Through a series of misfortunes, she becomes paraplegic. That is when Baam decides to become her legs instead, so that they can scale the tower together. Then it is subverted by Rachel trying to kill Baam, revealing that in fact she his completely healthy and the misfortunes were staged plans. After Baam's disappearance, she gets the support of their unwitting True Companions.
Kisara in Yu-Gi-Oh!. Seto saves her life twice, and she repays the favor in spades.

Film

The page quote comes from a scene in Serenity where Ill Girl Waif Prophet River takes on an entire army of Reavers alone, just to get a medical bag for her wounded caring brother. Good thing she excels at kicking ass.

She always did love to dance...

Murder By Death: ~~Miss Marple~~ Jessica Marbles is expected, along with her nurse. Enter a little old lady pushing an even littler older lady in a wheelchair - the one in the wheelchair is the nurse.
Slight variation: In Quest for Camelot, Garrett is blind and has a falcon companion who "is [his] eyes." At the end of the movie, Garrett and his love interest Kayley must navigate an Absurdly Spacious Sewer which is very dark. Garrett helps Kayley through the tunnel, telling her, "Don't worry, I'll be your eyes."
The second Spider-Man film—by the climax, Spider-Man has spent the past two movies protecting New York City, and has just saved a train from being destroyed. The citizens on-board carry the injured Spider-Man to safety inside the train and attempt to protect him from Doc Ock. Doc Ock gets past them easily, but the scene is still heartwarming.
In How To Train Your Dragon, Hiccup takes care of Toothless for a majority of the story, from bringing him food to helping him fly after losing part of his tail. By the end of the story, it's Toothless's turn to help Hiccup when Hiccup loses his left foot and hasn't adjusted to walking with an artificial foot yet.
A literal example of this trope appears near the end of The Return of the King in what could very well be considered Sam's Crowning Moment of Awesome

Sam: (hoisting Frodo over his shoulders) I can't carry it for you, but I can carry you!

Literature

In Ivanhoe, Rebecca nurses Ivanhoe back to health. Later he comes to save her from being burned as a witch.
Happens near the end of the Dragonlance Chronicles with Raistlin and Caramon.
In To Live, Fugui carries Jiazhen on his book when she becomes too weak to walk, leading in a Crowning Moment of Heartwarming when she tries to protest, and he tells her that he is showing his love for her.
The end of Cryoburn: Gregor asks to be a pallbearer at Aral Vorkosigan's funeral.

"The man has carried me since I was five years old," answered the Emperor of Barrayar. "It's my turn."

Live Action TV

In the second season of Buffy the Vampire Slayer, Drusilla is physically healed in the same episode that Spike is horrifically injured, and she says a line very like this. The rest of the season has their relationship entirely inverted.
Also, there's Kenneth and his mother: "You carried me for nine months, now let me carry you."
In Merlin, Mordred is glad to take care of an injured Morgana, in thanks for her previously caring for him.
- The first season is mainly made up of Merlin and Arthur repaying each other for the continual saving of each other's lives.
- Guinevere travels to Ealdor with Merlin to defend his home against bandits, telling him that it's repayment for the time he saved her from being executed as a witch. She ends up saving his mother's life.
- At the end of the third season, the future knights of the Round Table all pledge their fealty to Arthur for past deeds rendered toward them. It's especially touching since Arthur is asking them to help save his father, and many of them have good reason to hate Uther's guts.
Whenever a Companion shows up to save the Doctor's hide. Sometimes, they show up en masse.
"No, it's cause this guy fell into a hole, see?"
Often happened in understated ways betwen Robin and Much in Robin Hood. At one stage Much trips over and urges Robin to carry on.

Much: Don't worry about me!
Robin: I like worrying about you!

Doctor Wilson spends so much time caring for his maladjusted, emotionally crippled best friend that it's a wonder that he has time to practice medicine. Whenever Wilson faces a crisis, however, House will usually provide support—albeit in the most ass way possible.

Music

The Rolf Harris song "Two Little Boys"—when Joe and Jack are children, Jack breaks his wooden horse and Joe offers him a ride: "Did you think I would leave you crying when there's room on my horse for two?" Later, when they've both grown up and are cavalry officers at war, Joe's fallen to the ground and Jack picks him up on his horse, saving his life: "Did you think I would leave you dying when there's room on my horse for two?"
In the Vocaloid song "A Faint Wish", Rin tells Len that he has always been there for her and it's his turn to go on after seeing a long montage of times when Len has died for her.

Video Games

In Siren, Blind Seer Miyako has to use player character Kyoya's eyes to navigate around the stages during Escort Missions. Later on, well after the two get separated, Kyoya gets caught in a blacked-out room with a bunch of shibito standing between him and his goal. Then he hears Miyako's voice in his head, prompting him to use her eyes. This allows him to see the auras of the shibito and run past them in the darkness. It is revealed soon after that Miyako is already dead at this point, but she goes on to serve as Kyoya's Spirit Advisor for the Final Battle.
In BioShock (series) 2, Eleanor, after getting her Big Sister suit and breaking you out, basically says this as she's lifting you to your feet, "You Fought for me Father, Now let me fight for you".
In Ico, Yorda ends up carrying Ico to safety.
In the ending of Dissidia [duodecim] 012 Final Fantasy, when the Warrior of Light is at the brink of death protecting Cosmos from the Manakins, Cosmos unleashes her power and sacrifices herself to save him.
In "Metal Gear Solid4 Essentially all of the game's final act is the people snake helped throughout the series making last stands at various points in Outer Haven so that he can break into the server room. For all intents and purposes Raiden does this for his entire 4th title with one of his first lines being "Okay Snake, now it's time for me to protect you."

Real Life

It is and has long been common for elderly parents to be looked after by their children.
This is probably the aspect of the evacuation of Dunkirk which made it such a morale booster (to the extent that Brits will still boast about it to this day) despite ostensibly being a humiliating defeat—civilians who'd been reliant on the armed forces for so long were suddenly needed to literally carry them to safety.