ALWAYS SIX O’CLOCK by Phoef Sutton, G.P. Putnam’s Sons, 288 pages, $23.95 hardcover.

Imagine that you are 35 years old, still living in the California house in which you were raised, and are awakened in the evening by a strange sound — the rattle of pebbles thrown at a window. You go to the window in what used to be your room as a teen-ager and look out. There is your high school sweetheart tossing pebbles just as she used to do 20 years ago.

That’s how Mainer Phoef Sutton begins his romance and mystery novel “Always Six O’Clock.”

The romance for protagonist Carl Rooney is in the rediscovery of his young love, Jesse, and that’s the mystery — for Jesse thinks it’s still 1978.

So, Carl, Jesse and Carl’s co-worker, Kit — they’re both scriptwriters — set out to find out what happened to Jesse, who has no memory of the past 20 years.

It’s an intriguing plot, neatly developed by Sutton, himself a scriptwriter. This is his first novel, and it is a polished one, reflecting his background as a writer for the TV show “Cheers” and as screenwriter of “The Fan,” starring Robert De Niro. Sutton has two Emmys, a Writers Guild Award and a Golden Globe, so he’s hardly a stranger to writing.

He has a deft touch as Carl and Jesse go to where she used to live — but the house is gone. With a mixture of the macabre and humor, Sutton shows us a rekindled love in Carl and a black hole of memory in Jesse. But it is Kit, a type-case homosexual, who does some quick research and finds that Jesse was married and two months ago was lost at sea.

Now, as we would say in an old-fashioned melodrama, the plot thickens. A little reconnoitering is in order as Carl goes to where Jesse now lives and meets her husband, who thinks Carl knows something about Jesse’s “disappearance” and promptly tries to buy him off with a $20,000 check.

Now, Carl and Jesse must try to figure out why this husband might have tried to kill her, and to stir the plot even more, the brother of Jesse’s husband pops up, avidly in love with Jesse.

Sutton has a marvelous sense of pace as he works the plot through each of these developments with many more twists to come.

The screenwriter loves to tease the reader, as is obvious from the beginning. Before he even introduces the characters and plot, he precedes all with a brief quote of the scene in “Alice in Wonderland” where the Mad Hatter explains to Alice why “it’s always six o’clock now.” But then we are caught up quickly in the opening, and that reference is left behind. Even much later, when it is dropped lightly in front of us in a scene, we miss the connection. And, of course, that’s the book’s title.

For Jesse, this search through her recent past is bewildering. For Carl, it is nearly fatal as accidents and attempted murder dog him. But which one of the characters is the murderer?

Other than Carl and Jesse — Jessica Ackerman, to give her proper name — the characters are a bit thin. There is Martin, Jesse’s husband, a big man with a short temper; his brother, Wesley, who comes across as one of those mediocre people who seem to hover on the edges of a group; and, of course, Carl’s partner, Kit.

But, while the characters are thin, Sutton shows his strength in the scenes that he creates for us. There are revelations of the past, neatly worked into the plot. There are increasing threats to Carl and Jesse. And, there is poignancy too, as Jesse finds her mother in a nursing home and as Carl and Jesse relive their breakup of 20 years ago. And each of these ratchets the tension up a notch as we go along on the hunt for who Jesse really is, whether she survived an accident or attempted murder, and, if so, by whom?

The closing scenes are taut and action-packed.