Outside, a badly beaten Collins is discovered by Angel, a street musician. She offers bandages, comfort, and an invitation for a night on the town. They bond when they realize they are both HIV-Positive.
In the loft, Mark urges Roger to come out for the evening, but Roger refuses. Left alone, he stoically takes his AZT and dreams of writing one last song to redeem his empty life. He is interrupted by a beautiful stranger from downstairs, Mimi. Mimi needs a match because her electricity is out. She and Roger have an instant attraction, but Roger resists because Mimi is a junkie.
At last, Mark returns with Collins, who brings provisions and better-yet-funds, in the person of Angel, now decked out in glorious drag. Angel explains how he has earned a fast $1,000 which he is eager to share. Benny barges in with a deal: If Mark and Roger will stop Maureen's performance tonight protesting the clearing of a tent city from Benny's adjacent vacant lot, Benny will forgive Mark and Roger's back-rent. Once Benny is gone, Mark, Angel and Collins head out for the evening, leaving Roger alone again.
In the lot, Mark gathers his courage to meet the formidable Joanne, Maureen's new lover, who has also usurped Mark's stage manager duties. When Joanne reluctantly accepts Mark's technical assistance, the two quickly find common ground in their shared experiences of the self-centered, unfaithful albeit irresistible Maureen.
Angel and Collins attend an AIDS support meeting; Mark arrives to document it on film. The group affirms its determination to live without fear-"no day but today".
Meanwhile, in her apartment, Mimi is dressing to kill. Turning up again on Roger's doorstep, she implores him to take her out. Roger is tempted, but his fear ultimately compels him to push Mimi away. Simultaneously, a young support group member quietly asks, "Will I lose my dignity..Will someone care?" His questions are echoed by each member of the community, including Roger, who decides finally to leave his loft in search of answers.
In the lot, Mark, Angel, and Collins rescue a homeless woman from police harassment. The woman, however, is hardly grateful. Mark, Angel, and Collins fantasize about leaving New York behind to live the good life, far away. Mark goes to check on Roger, leaving Angel and Collins alone to declare their newfound love.
Joanne dials Maureen from a payphone simultaneously juggling two other calls on her cell phone. In St. Mark's Place, the homeless, sidewalk vendors, junkies, drug dealers, and cops comprise a human mosaic. Angel buys Collins an overcoat, Mark meets up with Roger, and Mimi hunts for a fix. Roger spots her, apologizes for his behavior in the loft, and invites her to dinner. She accepts.
Maureen arrives and presents her performance piece, a satirical protest that calls for a communal "leap of faith" against Benny's commercial development.
Afterward, everyone meets at the Life Cafe, where they hear a gloating Benny declare that Bohemia is dead. Mark and his fellow bohemians joyously reject Benny's pronouncement. Benny exits in anger, stopping only long enough to hound Mimi, who is, it would seem, a former lover. As her beeper sounds, Mimi pauses to take her AZT. Roger discovers that his secret and his illness are Mimi's also. Exhilarated and frightened, they resolve to assume the risk of romantic involvement as well.
Joanne has several times been ordered back to the lot by Maureen. Fed up, she finally rebels, announcing that their relationship is over. She also informs everyone that a riot has broken out on Avenue A. Benny has padlocked Mark and Roger's building and called the police. The bohemians continue to celebrate. The riot continues to rate. Roger and Mimi share a small, lovely kiss.
New Year's Eve. Mark films a "breaking back into the building party". Mimi and Roger are there and in love. Maureen humbles herself to earn back Joanne's favor. The celebration is complete when Collins and Angel arrive with a blow-torch.
Once inside, Mark discovers a phone machine message left for him with a job offer from a tabloid television show hostess named Alexi Darling. Benny crashes the party to ostentatiously apologize, offering the boys new keys to their old loft. Suspecting Benny's motives, Roger balks. Furious, Benny implies that Mimi helped change his mind by sleeping with him. Mimi angrily denies this, but the damage is done; Roger is bitterly jealous. Mimi is cornered outside by her dealer with a little something to assure her "Happy New Year."
Valentine's Day. Roger is living with Mimi, but remains terribly jealous, often threatening to leave. Angel and Collins survive together wherever they can. Mark still lives behind his camera. At their apartment, a warring Joanne and Maureen issue each other an ultimatum. Neither backs down-they split up once again.
Spring. Everyone feels the coming changes. The community asks: "How do you measure a last year on earth?". Roger walks out on Mimi, accusing her of being unfaithful with Benny. Alone, Mimi mourns the impending loss of love, while Collins nurses the increasingly ill Angel. The end of spring brings reconciliation for Roger and Mimi, as well as Maureen and Joanne, but all is tentative at best.
Summer's end, and Alexi is still calling, enticing Mark with big money. Much lovemaking is witnessed, framed by attendant frustrations in the age of safe sex. By the fall, Roger, Mimi, Joanne and Maureen are all on the outs again. Collins and Angel's separation, however, is profound and final. Angel has died.
At Angel's memorial each friend offers a loving tribute. Clutching the overcoat Angel gave him at Christmas, Collins reaffirms his undying love. Outside the church, Mark phones Alexi and accepts her job offer, despondent at how drastically life has changed since that Christmas night just one year before. As the mourners exit the church, Mimi learns that Roger is leaving town for good. A nasty scene ensues, with arguments erupting between all the estranged lovers. Collins, in sorrow, begs them all to stop. Maureen and Joanne are moved to try once again to reconcile. Mimi and Benny leave together.
Mark tries to convince Roger to stay in New York and confront his pain, but Roger lashes out, accusing Mark of also remaining detached, hiding behind his camera. Mark wonders whether Roger is simply afraid to watch Mimi die. Mimi appears and lets Roger off the hook, insisting that she has just come to say goodbye. Roger leaves for Santa Fe and Mimi begs Mark for help, Benny turns up and offers to pay for Mimi's drug rehabilitation but she refuses and instead runs away. When Benny covers the cost of Angel's funeral, he and Collins warm to each other and head off to get drunk as Mark prepares for his meeting with Alexi.
Mark questions the choice he is about to make and the world in which he lives. His thoughts are echoed by Roger on his way to Santa Fe. They both remember the beauty of last Christmas Eve, when they felt connected, and their friends were a family. Roger begins to discover his song. Mark turns down the TV tabloid job to finish his film.
Roger, Mark, Mimi and Joanne's parents all wonder where their children are as the holidays approach.
Another Christmas Eve. Mark has pieced together a rough cut of his film, which he hopes to screen tonight. Roger has moved back into the loft and has finished his song. No one has been able to find Mimi. The power blows again but the night is brightened by the arrival of Collins. Then Maureen and Joanne appear on the sidewalk below carrying a desperately ill Mimi.
Laid out in the loft, Mimi finally manages to tell Roger that she loves him. Begging her not to leave him, Roger sings his "one song" for her. "I have always loved you," Roger whispers, then cries out her name as Mimi slips away.
Moments later, however, she returns, with stories of a warm white light and Angel steering her back to life. Celebrating the wonder of life's terrible uncertainty, the community re-affirms love as the strongest force we know, acknowledging there is always, "No day but today."