The Soloist is one of those character-driven dramas in which little seems to happen, yet you leave feeling transported.

Based on a book by Los Angeles Times writer Steve Lopez, this tale of friendship between a burned-out journalist and a homeless schizophrenic prodigy has tremendous heart and is buoyed by terrific performances. The rich, emotional texture more than makes up for its sometimes heavy-handed direction and clumsy plot development.

Robert Downey Jr. plays Lopez, a disenchanted columnist who has run out of story ideas. While walking in a park, he is drawn in by the strains of a violin, and surprised when the musician turns out to be a homeless man playing with just two strings.

Nathaniel Anthony Ayers (Jamie Foxx) apologizes for his disheveled appearance as he babbles on, but his stream-of-consciousness ramblings make odd sense and intrigue Lopez. The reporter does some digging and finds out that Ayers once attended Juilliard as an aspiring cellist before dropping out for reasons unknown. Lopez writes about Ayers, and as the columns attract attention the men become inextricably attached and help each other to battle their demons.

In 2008, Lopez published a memoir based on earlier columns about Ayers that encompassed various aspects of their relationship, including racism, mental illness, homelessness, friendship and the redemptive power of music. In an effort to mesh these themes, British director Joe Wright (Atonement), working from a screenplay by Susannah Grant (Erin Brockovich), create a narrative that is sincere and compelling, but structurally a bit loose.

At times, flashbacks into Ayers’ past work well; at other times they come across as a clich éd plot device. A scene in which a renowned music instructor (Tom Hollander) fanatically rants at Ayers seems overly contrived. And the invention of Lopez’s editor ex-wife (Catherine Keener) does little to add to the proceedings, especially when you consider that in real-life Lopez is happily married.

The Soloist is at its best when Wright keeps the camera focused on Downey and Foxx, which, thankfully, is much of the time. Both actors are masterful in their respective roles; Downey imbues the seasoned journalist with a convincing blend of jadedness, curiosity, intensity and compassion, while Foxx is downright astonishing as the homeless virtuoso. Watching the actor is mesmerizing as his Ayers, dignified and semi-lucid, whose cadence is as poetic as it is jarring, ricochets between bursts of brilliance and despair.

To the filmmakers’ credit, the movie offers no easy or inspirational ending. And while The Soloist makes noise about the plight of the homeless and mentally ill in this country, it’s the unlikely connection between two lost souls that has the loudest impact.

The Soloist opens Friday, April, 24. Rated PG-13 for adult themes and language.