In the film, Stella (Haley Lu Richardson), a teen meticulously managing her cystic fibrosis, meets Will (Cole Sprouse), a boy with the same genetic disorder who takes a more relaxed approach to his medical regimen. Stella — who admits she has control issues — attempts to make over Will’s medical plan, and, along the way, the two teens fall head over heels for one another.
The only issue is that Stella and Will can never actually touch — or even be within six feet of one another, due to the fear of cross-infection. A big, epic kiss (the climax of many a romantic drama) is firmly off the table. If Stella catches Will’s bacteria, or Will catches hers, either could die, which is assured to them by Nurse Barb (Kimberly Hebert Gregory) who has seen this very thing happen between two teen lovers in her care.
Stella and Will are pretty good about this rule (though they do steal one foot back, hence the title of the film) until Stella’s best friend and fellow cystic fibrosis patient Poe (Moises Arias) dies. Overwhelmed with grief, Stella demands Will go with her on a snowy stroll through the park to see the lights of the city that she has been limited to gazing at from the hospital roof.
While hanging out on a frozen lake, Stella and Will almost kiss — but Will pushes her away, reminding Stella that they can’t do this for their own health. It’s moments later Stella gets the call that there is a brand-new pair of lungs waiting for her at the hospital...should she show up to claim them. Heartbroken over Poe and frustrated with all she can’t do, Stella ignores the call, which frustrates Will.
Then, while on the bridge above the lake, Stella falls, sending her body plummeting through the ice and into the water.
Will pulls Stella out, but she’s not breathing. The only choice? Perform mouth-to-mouth...aka, the very thing that could put Will and Stella in grave danger.
Stella and Will are rushed to the hospital, where she receives her new lungs. Will learns from Barb that, by some miracle, Stella did not catch Will’s bacteria — though it doesn’t mean she won’t suffer consequences from their “forbidden kiss” down the line. As for Will, the experimental drug he’s hoped would save his life isn’t working...which means that Will’s time is running out.
Will realizes that he has to say goodbye to Stella. So, he gives her one final parting gift: the “lights” of the city that she wanted to see on their snowy walk. He creates a beautiful art installation, then tearfully tells Stella (through the glass of the recovery room where she lies following her lung transplant) that she has to continue to live, even if he won’t be around. And, of course, the two share “I love yous.” (Though, by this point, you may be a blubbering mess and miss them over the sound of your own sobs.)
We don’t see Will’s death, but it’s heavily implied that he will not survive for much longer, and that Stella is reflecting back on her time with him. However, in Cole Sprouse's interview with Refinery29, he insists that, ""We wanted to keep the ending open for interpretation," which means that, technically, Will could survive his illness...even if it's not with Stella. In fact, a happier ending may even exist.
"We actually filmed a lot of different endings," Sprouse tells Refinery29. "A lot of people who saw the movie assume that he lived. It’s intentionally open. I won’t speak too much about it because I want people to have their own feelings about it, but yes, we filmed a handful of different endings, and some endings were more concrete."
Whether Will does survive CF, the tragedy, of course, remains: Will and Stella cannot be together without putting the other in danger. However, the movie makes clear that the love they share can never truly die.