I would watch Benedict Cumberbatch (top) and Kelly Macdonald (top) as the lead team in a needlepoint circle if they were appearing there.

With this in mind, I found it challenging to watch them as the lead players in The Child In Time, a British movie airing Sunday at 9 p.m. ET (check local listings) on PBS’s Masterpiece series.

Cumberbatch and Macdonald play Stephen and Julie Lewis, the happy parents of a toddler daughter, Kate, on whom neither can dote enough.

One day Stephen takes Kate to the store to make a small routine purchase. During the minute it takes him to pay at the register, or maybe it’s less than a minute, Kate disappears.

The little girl in the yellow coat is gone. No one in the store has seen her. The police can’t find her. There are no clues.

Life as the Lewises knew it is over.

Julie asks Stephen how this could have happened, which is the same question he asks himself. They don’t know who to be angry at, so Julie gets angry with Stephen and Stephen withdraws into a world where every minute of every day, on some level, he’s looking for a girl in a yellow coat.

Ian McEwan’s prize-winning 1987 novel, on which this adaptation is faithfully based, though it must compress some of the subplots, differs from many other missing-child stories.

In most of those, there will be a resolution. In this one, there might be. Or maybe not.

Instead, it focuses on what an unthinkable event like this can do to a parent’s psyche, which in this case mostly means Stephen’s.

As time passes, we learn Julie has left. We still see her, and Macdonald fills us in nicely on how she has adjusted her life, but we know that she and Stephen, after a time, could not continue living together with this weight pressing down on them.

Stephen, on some level, gets back to his work as a writer. He also starts to experience something that falls between flashbacks and visions. He sees himself as a child. He sees his mother. In a sense, as the title suggests, Kate becomes an element in the passage of time.

Meanwhile, the man who has helped keep Stephen sane and functioning, Charles (Stephen Campbell Moore, right), has left his position as a book editor and then a national legislator to move into the country.

This isn’t alarming in itself, but his behavior increasingly becomes bizarre and disconnected, making Stephen’s life even a bit more surreal.

As all this suggests, there are passages when The Child In Time becomes quite dark, which is the challenging part of watching it. It’s pain without remedy.

The performances are first-rate and the emotions feel genuinely raw. The discomfort and tragedy of the situation feel both honest and depressing, particularly because we are given no indications where the story could end. Or whether it will end at all.

Hint without a spoiler: It does.