Christopher Shinn, who wrote this drama at 23, is wise beyond his years when it comes to sexual yearning and its repercussions. Previously produced in New York and Chicago and by London’s Royal Court Theatre, Four follows two interracial odd couples on the Fourth of July: Gay high school student June (Keith Nobbs) is on a date with Joe (Isiah Whitlock Jr.), a married black professor whom he met on the Internet; and Joe’s articulate teen daughter Abigayle (Pascale Armand) spends the evening with half-white, half-Latino basketball player Dexter (Armando Riesco). Shinn’s dialogue is dead-on, and Manhattan Theatre Club’s ace cast makes it sound utterly believable. Now, if only it packed dynamite. Four ends with fireworks but never becomes truly explosive.