When it comes to documentaries, I like them as tightly focused as possible. Sometimes a look at a single apartment complex can open a window on an entire world. The “Independent Lens” (9 p.m., PBS, check local listings) film “At Home in Utopia” does just that.

“Utopia” recalls a group of apartments built in the Bronx in the 1920s. For poor immigrant Jewish laborers, the United Workers Cooperative Colony, known as the Coops, was a piece of the American Dream. But “Utopia” shows us that the American Dream is also a reflection of the dreamers. And most of these idealists were dedicated members of the American Communist Party.

For these folks, Russia was no abstraction. Many had escaped cossacks and murderous anti-Jewish pogroms. So a revolution that deposed the czar and claimed to speak for the workers was A-OK.

“Utopia” doesn’t argue for or against their politics, but does a wonderful job of showing what it was like to grow up in an insular and isolated subculture, cut off from the attitudes of “normal” Americans.

Women now in their 80s recall when their public-school teachers asked why they weren’t taking off the Jewish High Holy Days. “May Day is our holiday!” they replied. Beaming with pride and affection, another elderly man remembers the day an FBI agent tried to interview his mother. “She spit right in his face.”

It wasn’t easy being singled out by police and strangers for living in “Little Moscow,” but there were also social clubs, basketball, jitterbugging and dating.

The 1939 Hitler-Stalin pact and Khrushchev’s 1956 revelations of Stalin’s policy of mass murder broke the hearts of many of the faithful and served to destroy much of the Communist fervor at the Coops. Cars, prosperity and the suburbs also beckoned.

• The six-part documentary series “Dallas DNA” (9 p.m., Investigation Discovery) follows a team in the Dallas district attorney’s office that uses DNA technology to exonerate the wrongly convicted and confirm the guilty. In the pilot episode, a man who has spent 26 years behind bars serving a life sentence for rape awaits justice that might come in the form of a simple cotton swab.

• Five years after the “Frontline” (8 p.m., PBS, check local listings) story “The New Asylums” recounted the staggering number of untreated mentally ill citizens behind bars, “The Released” follows what happens to them when they regain their liberty and attempt to re-enter society unsupervised, untreated and largely unmedicated.

Tonight’s other highlights

• The top five sing to survive on “American Idol” (7 p.m., Fox).

• Witness protection fails to save a turncoat mobster on “The Mentalist” (8 p.m., CBS).

• A freak killer covets spinal-cord fluid on “Fringe” (8 p.m., Fox).

• Typhoon winds and mournful tales cast a pall on “Deadliest Catch” (8 p.m., Discovery).

• Fresh from writing a political exposé, a journalist vanishes on “Without a Trace” (9 p.m., CBS).

• Gail O’Grady guest stars as the distraught grandmother of a missing child on “Law & Order: Special Victims Unit” (9 p.m., NBC).

• Trevor sets a Mardi Gras love trap on “Cupid” (9 p.m., ABC).

• Tommy discovers holes in Jimmy’s story about a crucial event on “Rescue Me” (9 p.m., FX).