Leo, a 21-year-old lefty — “Marx was cool,” he says, and he doesn’t mean Groucho — did not need training wheels to bike 4,000 miles to see Grandma, a fellow lefty nearly 80 years his senior. But he’s still on training wheels in life.

Vera and Leo are emotionally needy as we meet them in Amy Herzog’s critically embraced Off-Broadway play “4000 Miles,” making its Long Island premiere, tenderly directed by Sarah Hunnewell for the Hampton Theatre Company. Pulitzer jurists made “4000 Miles” a 2013 finalist for drama. The prize went to “Disgraced,” Ayad Ahktar’s explosive play about a Muslim-American’s identity crisis.

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Nothing so dramatic as a crisis occurs in this character-driven play in which not much happens beyond conversation and a kiss. The power of Herzog’s play lies in compassion disguised as listening.

At the end of a harrowing transcontinental trek, Leo shows up at Vera’s Greenwich Village apartment, rendered with a touch of the past by Sean Marbury. Averse to cellphones, Leo hasn’t called his mother. He was to have been accompanied on the odyssey by his three best friends. Injury sidelined one young woman while Bec, his girlfriend, backed out citing personal and academic excuses. Leo and his buddy started out from Seattle. But Micah died in Kansas.

Diana Marbury plays Vera with a feisty, grudging acceptance of the reality of advanced age. Her body and sometimes her mind — “I just hate it when I can’t find my words” — remind her constantly. All her friends and both husbands are dead. Her stepdaughter’s family, including Leo, live in Minnesota. Marbury, through body language and a faltering struggle to express frustrations and spout opinions, lets us feel for Vera even as she repels pity.

Ben Schnickel as Leo, whose career so far is finding himself, exudes a cocky assurance that masks insecurities and a sense of loss he shares with Vera. Of his grandmother, he says to a girl he tries to bed (deliciously drunk as played by Samantha Herrera), “She’s like a really good friend I happen to be related to.” That’s after Bec breaks the news to Leo that they’re breaking up, conflictedly delivered by Amanda Griemsmann.

Grandma and grandson trade stories about their sex lives over marijuana, and Leo reveals stark details about the bicycle tragedy. Even this traumatic monologue is leavened by the funniest line in this endearingly human play.