One of the first lines you’ll hear is “I could kill a fag right now.”

Don’t get up to leave. Simon Stephens’ ON THE SHORE OF THE WIDE WORLD isn’t homophobic at all. His play simply takes place in lower-middle-class England where a teen named Sarah is desperate for a cigarette and uses the famous British slang word for a tube of tobacco.

On the other hand, you might have missed this line because you might have been impressed by the exceptionally skillful dialogue Stephens provided at the very start of the play.

For after Alex tells Sarah “Have a guess” and she says “A million miles,” he shakes his head and says “Ninety-three million miles.”

Now we know that Alex is the smarter — and that Sarah doesn’t know a few things under the sun that most people do.

All this in three lines.

As the conversation continues, Sarah does reveal that she’s more street-smart. So there’s genuine dramatic irony in the following scene when Alice — Alex’s mother — says to her husband Peter that she believes that Sarah is “quite shy.”

Then we’re off to meet Peter’s parents Charlie and Ellen. For the next two-hours-plus, we have, to paraphrase the opening lines of ROMEO AND JULIET, two households, both alike in not having much dignity.

Tolstoy’s famous statement that “Every unhappy family is unhappy in its own way” is easily borne out here.

A true surprise comes a third of the way through the 150-minute drama, when one character leaves the stage for good. Given that the individual and the performer were making a strong impression, the audience almost feels as much pain as most everyone else on stage does.

To this point, Stephens was ostensibly taking us in a certain direction and building a character before he took this hairpin turn. That doesn’t necessarily mean bad playwriting; his plan is to show that life takes extraordinarily unexpected twists and there’s little-to-nothing that we can do about them.

For a while, the play seems to meander and threatens not to jell into one coherent whole. There are times when it seems to be about latent pyromaniacs and at others wants to warn that if you don’t have a profligate sexual past, when you’re older you’ll be haunted by what you missed (or think you’ve missed).

Eventually we catch on that Stephens just wants to show us a rotting slice of life. Such a simple line as “The whole business of, you know, being alive is very complicated” gets a laugh from theatergoers. They came to terms with that situation long ago, and they’re surprised that the character is so late to the funeral.

ON THE SHORE OF THE WIDE WORLD won the Best Play Oliver in 2006. So why wasn’t there enough interest in bringing it to our shore a year or two later as is the happy fate of most serious British hits?

It might not have arrived at all had Stephens not written THE CURIOUS INCIDENT OF THE DOG IN THE NIGHT-TIME. It opened on Broadway in 2014, received raves, won five of eight Tonys including Best Play, ran a month shy of two years – enough to make it the longest-running play to open this millennium. When such a success happens, producers and artistic directors tend to ask the playwright “What ELSE do you have?”

That may be a simplistic and unfair assessment. Atlantic Theater Company artistic director Neil Pepe could have read the play and thought “Hmm, I think I can bring something to this.”

He indeed has. No small part is his choosing a top-notch cast (although Wesley Zurick as Alex’s brother Christopher seems older than the 15 he claims to be).

Peter Maloney saddens us with Charlie’s gentle but probing question to Ellen: “When was the last time you wore clothes for me?” Blair Brown shows that Ellen has other issues. When she asks him

“Have you ever done something, or thought something, or acted in some way and known that afterwards your whole life would never be the same again?” we assume she’s made her point. No: Brown understands what Stephens is getting at when she adds “‘Cause I don’t think I have for a long time.”

Amelia Workman, playing Susan, the homeowner who’s hired Peter to renovate, makes us smile in how she delivers Stephens’ thought-provoking observation that people in photographs “don’t look like real people.” Tedra Millan manages to seem sincere when she tells Alex’s parents that she’s glad to meet them.

Many plays have reminded us that parents who give birth to a child are ultimately creating their future judge and jury. Yet considering that grandsons and grandfathers far more often than not exchange unconditional love, Alex’s castigation of Charlie makes the scene fresh and unexpected. Ben Rosenfield smartly does it with the justice of a Solomonic judge rather than by bald emotion.

Mary McCann’s Alice must deliver the tough speech where she reveals which of her sons she prefers. Under the circumstances that we’ve been given to this point, we’re surprised at her choice.

Alice is approached by John, with whom she has good reason to never speak again. She will, however reluctantly and then less reluctantly. None of this stresses credulity, partly because Leroy McClain is so earnest that his sincerity becomes persuasive.

In one scene they are subverted by Scott Pask’s set. We’ve been increasingly forced to accept economically spare scenery in these expense-laden theatrical times, but how Pask has handled one moment inadvertently gives rise to a red-herring.

Deep in the second act, Alice and John are sitting in the dinette set which has been established since scene one as her kitchen. That she’s asked him into her home suggests that she may be interested in taking him to another room. So aren’t we surprised when he looks off-stage and asks for a check?

All Pask had to do was fly in a tiny sign that sported the name of a café so that the audience not be misled. There’s a profound difference between a married woman meeting a man for coffee in a public restaurant and bringing him to her private residence.

As fine as everyone is, C.J. Wilson’s Peter is the most full-bodied interpretation. Wilson tenderly reminds us that in all our lives, we all have a person that we’ll never forget. That usually means someone we now think we wanted to have and hold from that day forth but foolishly let slip through our fingers; here Peter gives us a completely different reason why he’ll always remember Susan. No many how many what-might-have-been stories you’ve heard, this one may touch you the most.

Both Wilson and Maloney wonderfully underplay the important scene in which Peter tells his hospitalized father that he must leave now because visiting hours are over. Both know that he’s not concerned about the hospital’s rules; he’s seizing the chance to get out of there and not be blamed for it.

Many plays open with the playwright, as they say in the trade, figuratively “setting the table” for what’s to come. ON THE SHORE OF THE WIDE WORLD actually ends with characters literally setting the table. That’s it – people silently put plates, knives, forks and spoons in their traditional places as the lights dim.

Stephens may well have chosen this quiet ending to show that these lives are doled out in spoons no bigger than J. Alfred Prufrock’s. And yet, plenty more happens here that these characters wished they were encountering and enduring.