Antonio Banderas, Trudie Styler and Eva Birthistle on the Sorrow and Joy of TIFF Medical Dramedy ‘Up Against It’

When it comes to “Up Against It,” a TIFF title premiering Sept. 12, director Trudie Styler says, “I know this story like the back of my hand.”

She means that doubly. Not merely had she been mulling whether or not to take on the screenplay for years, and participated in workshopping it (including changing its setting from the U.S. to the U.K.), she also has a deep sensitivity to its subject matter. The film takes place in large part in a hospital, and Styler’s sisters are both nurses. “It’s a calling, isn’t it?” she muses. “It’s a calling to want to become a family member to the families who are struggling the most.”

In “Up Against It,” Styler summons that empathy and transmits it through the screen. Here, Álvaro (Antonio Banderas) and Saffron (Eva Birthistle) are the disharmoniously broken-up couple who share a single interest — their daughter, Rose (Eden Hamilton). When Rose’s oncologist informs the parents that she may need a sibling as a potential donor to keep Rose alive, Álvaro and Saffron must put their vanities aside and get to the hard work of reconciling — at least for as long as it takes to conceive a child.

The film maintains a laughter-through-tears tone that might seem difficult to keep from outright collapsing. “There is a sense of responsibility,” Banderas says, “but at the same time, what you cannot do is get too solemn about the thing — because life is not like that. In most circumstances, humor may appear.” Many of the jokes emerge through the slow thaw of Álvaro and Saffron’s enmity; it spoils little to say that the two have more in common than they might have thought in the heat of their disagreements.

“It’s quite an Irish thing,” says Birthistle, perhaps best known for her role on the TV series “Bad Sisters.” Humor, for her, is a coping mechanism: “Otherwise, it could get so bleak, and so hard. It’s just a way of going — let’s keep the jokes going.” She notes that her character, like Banderas’, is obligated to keep a sunny, happy face on to shield their daughter from her parents’ fears: “Saffron has no choice but to be OK. I’ll take it because I have to. But I think she goes home and sticks her face in the pillow and screams, and opens a bottle of Champagne.”

The small miracle of “Up Against It” may be that it keeps the parents’ emotions in mind without miring itself in fear — it’s a film about a critically ill child that manages to stay aloft. Part of that is the careful attention paid to Álvaro and Saffron’s relationship, which continues to unfold throughout. “They hate each other — or they think they hate each other,” Banderas says. “But then we discover that it’s not exactly like that. There is a supreme truth that flourishes.”

And part of it, as well, was Styler’s confidence in the material. “I’m not known for being a director,” she says. (An accomplished producer, Styler has previously directed one feature, 2017’s “Freak Show.”) “But nobody knows this story like I know it. And I have the confidence of being a producer for so many years to say, I’m going to lay this out.” Styler presented Banderas, an old friend, and Birthistle, a new acquaintance cast close to the start of production, with their character arcs, and then told them to let loose: “You always bring your arsenal to the character — life’s blows that you’ve suffered. All I can do is talk them through the arc that I’m directing, and they just got each other. That is kismet.”