Danika Merrick (Marisa Tomei) suffers from increasingly disturbing, paranoid hallucinations. Most of her hallucinations involve threats to her family and media-fuelled fears such as child kidnappings, car accidents, her children lying and terrorism. Danika confides to her husband, Randy (Craig Bierko), and Evelyn (Regina Hall), her psychiatrist.
The movie begins with Danika apologizing for being late, being scolded by her bank manager about incorrect calculations. Her manager leaves the office instructing Danika to remain there until errors are corrected. Danika then witnesses a bank robbery in progress with two trigger-happy robbers shooting anyone that moves. The alarm activates, and the robbers force Danika's boss to tell them where the security monitors are located. The manager points to her office where a shivering Danika seeks shelter in a corner. As the door opens, she expects to come face to face with a gun-toting bank robber, but is confronted by her manager who wonders what is wrong with her.
The movie continues with increasingly paranoid hallucinations, due to schizophrenia, including seeing a little girl in front of her daughter's school being pulled away by a suspicious-looking man as she asks Danika to help her; Danika does nothing only to watch in horror as the same little girl's mother appears on the news begging for her child's safe return. Danika also finds a human head in a grocery bag as she's putting the groceries in the fridge. She's oblivious as, standing in front of the school looking for her daughter who ran off, her daughter's teacher is killed by falling glass, (it turns out it's the same person's head she found in the grocery bag a day before). She also believes her son's partner for a school assignment is trying to give him AIDS, after she imagines the girl crawling into her bed and confessing she is dying from AIDS and is going to give it to Danika's son.
Near the end of the film, the audience learns that Danika was in a car accident years earlier while driving her young children home and she makes a side visit to see Randy. The accident occurred immediately after Danika found out he was having an extramarital affair with the children's nanny in a motel shower. Did her husband's extramarital affair cause Danika to crash? Or had she had a psychological break before learning of her husband's tryst? Danika's vision of the nanny is that of her psychiatrist who's been treating her. The nanny reveals that both she and Randy thinks that Danika needs serious psychiatric help because her behavior is dangerous to her children. Danika slaps both Randy and the nanny and drives away with the children in tow. In the car accident, all of Danika's children die, leaving Danika, (and, of course, Randy who was back at the motel), as the sole survivors. It can be assumed she never saw Randy again and which he probably blames the tragic death of their children on Danika and her "visions."
As the film ends, a homeless Danika sits on a bench at the scene where the accident occurred, basically reliving the events of that day, presumably every day. She slowly walks away pushing a shopping cart filled with her children's belongings. All the events after the accident—reuniting with her husband and raising her children to adulthood, are hallucinations Danika experiences, caused by the tremendous guilt she feels for running the red light that led to her children's deaths.
The film is directed by Ariel Vromen and written by Joshua Leibner. Danika's budget is estimated to be $5,000,000. "Danika" saw its world premiere at the 2006 CineVegas Film Festival in Las Vegas. At the San Diego Film Festival in 2006, the film picked up awards for "Best Film" and "Best Actress", the latter won by Regina Hall.