The best work of cinema coming out in the next few days won’t be in theatres or even streaming. It’s a screenplay, titled “A Summer Diary,” by Kathleen Collins, and to read it is to experience an extraordinary creation that, due to calamitous circumstances, is missing only the finishing touch of actually being made into a film. The screenplay appears in a collection of Collins’s writings “Notes from a Black Woman’s Diary,” which is coming out next Tuesday. Edited by Collins’s daughter, Nina Lorez Collins, the collection includes short stories, a fragment from an unfinished novel, diary entries, letters, plays, and two film scripts—this one, as well as the one that she wrote for “Losing Ground,” the only feature that she directed.

“Losing Ground”—filmed in 1981, completed in 1982, and scarcely shown at the time—was only recently rediscovered and given its much belated theatrical release in 2015. It reveals Collins to be one of the most accomplished and original filmmakers of her time. She was among the few black women to make a dramatic feature in the eighties, but she died, of breast cancer, in 1988, at the age of forty-six, without making another. “A Summer Diary,” which is, in effect, that second feature, extends Collins’s cinematic legacy. The two screenplays take up more than half of “Notes from a Black Woman’s Diary.” The entirety of the book joins her collection of short stories, “Whatever Happened to Interracial Love?” (published posthumously, in 2016), in proving that Collins was a polymath and an artist of extraordinarily diverse and original talent—simply one of the great artists, both literary and cinematic, of her time.

Born in 1942, Collins became a civil-rights activist while a student at Skidmore College. She earned a Ph.D. in French literature, worked as a film editor, and taught film at C.C.N.Y. She wrote short stories and a novel, though perhaps her most prominent public identity was as a playwright (her three-act play “The Brothers,” published in “Notes from a Black Woman’s Diary,” was staged in 1982 and reviewed high-handedly by Frank Rich in the Times). In “Losing Ground,” Collins filmed the story of a professor of French philosophy at C.C.N.Y., Sara Rogers (played by Seret Scott), who is married to an artist named Victor (Bill Gunn). As they take a summer house in the country, she is embarking on a book about the concept of ecstasy but is frustrated that her work itself isn’t ecstatic—and when a student (Gary Bolling) invites her to act in his thesis film alongside his uncle (Duane Jones), a professional actor, she finds an opportunity to experience ecstasy artistically.

Collins said, in an interview, that her cinematic model was Éric Rohmer; like his films, “Losing Ground” presents taut surfaces of dialectical wrangling in workaday situations and reveals the passions roiling beneath them. As in Rohmer’s films, there’s a sexual aspect to that passion, but in “Losing Ground” there’s more: Sara notes that her experience of blackness has little place in the philosophy department and not much of a role in her work, and the artistic discovery in which she takes part—a choreographed musical reworking of the legend of Frankie and Johnny—is a reclamation of the mythological power of her heritage. Also, the distinctive experience of the social and psychological burden of being a woman glimmers throughout the film and ultimately bursts forth in action that’s both dramatic and richly symbolic.

Collins’s stories and dramas address these themes frankly and imaginatively, with language that’s as creative as her sense of literary structure. In the transfiguration of early troubles in the story “Scapegoat Child,” she writes, “All these folk are Negroes what dark brooding what hopeless feelings underpin the already cruel family landscape who can say but all these folk are Negroes.” The story “Nina Simone” presents a white man, the black woman who’s married to him, and her black male lover, all speaking in their own voices. The intensely sexual story “Raschida” features voices within voices, as does the fragment of her novel “Lollie: A Suburban Tale” (which is the story of a white couple, a writer and a psychiatrist, who befriend a black musician and a black singer). In an extraordinary letter to the seventeen-year-old Nina, Collins writes, with anguished and lyrical profundity, about women’s experience (“The terribleness is not vengeance but the irreparable damage to that well-spring that I sense to be peculiarly feminine, a well-spring that, quite literally, at its best, rises up and floods life with love and light and a capacity to give that is shimmering.”).

Even the excerpt from Collins’s own diary is multilayered and polyphonic—in effect, a meta-diary—featuring a 1975 entry about her rereading of her old diaries, which she herself excerpts and comments on. Her plays have a similarly intricate sense of voice and rhetoric. In “The Brothers,” none of the brothers are seen directly—instead, the four black men, some prominent and successful, others devastated and woebegone, are portrayed from the perspective of their wives, their sister, and the mother-in-law of one of them, in a series of interlocked tales, present and past, anchored by the presence of an undertaker in a funeral parlor.

By contrast, Collins’s film “Losing Ground” and her script for it are conspicuously straightforward and classical (which are also Rohmerian traits). Although the plays are grandly declamatory and, at times, abstracted and allusive, the script for “Losing Ground” is terse and compact; it’s a tale that doesn’t call attention to the telling. Collins films it with a luminous naturalism that’s ardently attentive to location, gesture, inflection, dress, décor. It’s also a traditional film script, replete with the codes of the trade, such as indications of medium shots, long shots, closeups, and cuts; notably, the most frequent indication is “P.O.V.,” point of view: the shifting perspectives that take an almost architectural form in Collins’s stories and plays are conceived to be dispersed like threads throughout her movie.

It’s precisely in this only seeming artistic modesty that Collins asserts her directorial design. The secret to the script of “Losing Ground” is that the ecstasy does not just belong to the character of Sara; it’s also that of Collins herself, in the sheer sublimity of combining seeing with being, witnessing with creating. The film is no mere recording of scripted action but a discovery of the fullness of being of the actors, the places, the very ideas that, in graceful touches, she puts into the world. The script’s classical precision carries a philosophical orientation; in its clarity and spareness, it seems to have its windows open for light to come in and for Collins to look out. It isn’t only in the choreographed dance and the fervent drama but in simple and unadorned moments, as at a pay phone or a verdant yard, that her visual ecstasy bursts forth. It’s as if her script were no blueprint but an appointment book for encounters of vision—both outer and inner.

In “A Summer Diary”—which begins with the note “All the characters are black”—Collins expands on this vision and also on its essentially literary origins. (Nothing in the book indicates whether this script was written before or after “Losing Ground.”) “A Summer Diary” is another story of city people in the countryside—the story of two women in their thirties, best friends, Caroline and Liliane, each of whom has two young children. Together, they rent and move their families into a big, ramshackle summer house, an hour from the city. Caroline, a set designer in the theatre, has a daughter of about five and an infant son; Liliane, a weaver and couturière who hand-makes clothes to order, has a boy of seven and a girl who’s also about five. Caroline is married to Rafael, a former artist who has become a successful investment counselor; her summer in the country is part of their trial separation. Liliane is recently widowed—her husband, Giles, committed suicide.