An excellent script and superb acting by Casey Affleck and Michelle Williams make “Manchester by the Sea” the deeply moving theater experience it is. Written and directed by Kenneth Lonergan, “Manchester by the Sea” is an in-depth exploration of death, grief, loss and love.

Affleck portrays Lee Chandler, a janitor/jack of all trades for four apartment buildings in Quincy, Massachusetts. By way of introduction to the character, we see him interacting with some of the tenants as he handles repairs and tenant personalities (that sometimes push him just a bit too far); watch him silently shoveling his walkway; we go with Lee to the local bar where he gets hammered and starts fights; we see him sitting in his one room “apartment.” His is a solitary existence.

One day he gets the call none of us wants to answer A family member has been hospitalized and is not expected to survive. Lee drops his shovel and drives 90 minutes to Beverly, but he arrives too late to say goodbye to his big brother Joe who died an hour earlier of congestive heart failure. Lee is greeted by longtime friend George (C.J. Wilson) who fished with Joe and was with Joe when he had the heart attack.

A series of memories flood Lee's mind, more than usual, once he returns to Manchester. His hometown. These memories tell us Lee's back story, wave by emotional wave. It's through a memory we learn that Joe had been diagnosed with heart disease some years earlier.

When Lee leaves the hospital, he heads to Manchester's middle high school. He must tell Patrick (Lucas Patrick), his nephew, that this time, this trip to the hospital, his father didn't make it.

The next day when Lee sees Joe's attorney about the will he learns that his brother made him Patrick's guardian. Joe even had money to support Lee as he got resettled in Manchester — in Joe's house — and to pay for his moving costs. Lee is stunned and tells the lawyer he cannot be the 16-year-old's guardian and that he cannot live in Manchester again.

As he tries to come up with a solution, Lee does in fact move out of Quincy and stays at Joe's with Patrick. Lee learns his nephew is a hockey player, a ladies man in the making, and a guitarist in a punk rock band. He also learns that Patrick does not want to move to Boston. Patrick suggests living with his mother, an alcoholic, who his father divorced when Patrick was about 7 or 8. Uncle Lee says that will never happen. Joe wouldn't have wanted it.

Being back in Manchester, Lee struggles to keep it together. The personal tragedy that drove him away is inescapable now. Every corner, every street, every everything reminds him of his heartbreak. Cue the tears.

Lee's ex-wife Randi (Michelle Williams) calls Joe's house a day or so before Joe's funeral to see how Lee and Patrick are doing. And to see if it's OK with Lee if she — and her husband — come to the service. Sure. No problem. You should be there, Lee tells her.

Lee runs into Randi after the funeral one day while he is out looking for work. Randi is taking her newborn son for a walk along with a girlfriend. I can't say much about what happens here without giving away a most significant plot line. Except for one thing: their interaction in this space and time is pure raw emotion — but not the over the top, melodramatic kind. It's real. You can feel the intensity of the moment as it is being experienced by Randi and as it is being experienced by Lee. And the tears, they will fall.

After announcing I was going to see “Manchester by the Sea” last night on my Facebook page, a friend wrote “I'll bet you cry.” And I did. Many times.

And so might you.

What is it about Affleck's performance?  It’s true; true to the character he is portraying considering the tragedy and guilt Lee has had to endure and will endure for evermore. Affleck communicates much often without speaking. When he arrives at the hospital and learns of Joe's death, the processing and emotions rising internally is outwardly understated, but is keenly felt by an audience. Casey Affleck recently won a Golden Globe for Best Performance by a Male Actor in a Leading Role.

Williams' performance is equally as true — and equally as powerful as Affleck's … I cannot say more without giving things away. Suffice it to say, Michelle Williams is one of the best actresses of her generation. She, too, won an award for her performance as Randi Chandler — The New York Film Critics Circle Award.

This is a film that must be seen. Or, as one of the characters might say, “Go see the “effen” movie already! Get in your “effen” car and go!”

“Manchester by the Sea” is playing at The Harbor Theatre in Boothbay Harbor. Showtimes for this R-rated film are 7 p.m. Thursday, Jan. 12, Friday, Jan. 13, Saturday, Jan. 14, Wednesday, Jan. 18 and Thursday, Jan. 19, with a 2 p.m. show on Sunday, Jan. 15.