SPOILER: It occurs to me after watching a dozen or so episodes from the boxed set that some of them aren't what anyone would call inspired. I don't mean this one necessarily, but some others are pretty flat.
This episode isn't uninteresting. Barbara Belgeddes is always appealing in a winsome way, not quite Hollywood gorgeous but intimating good breeding. Sounds like she went to Bryn Mawr or someplace.
She's engaged to a dull bulb but drops him when she meets Michael Rennie at a formal ball. He waltzes her around and takes her out on the balcony for a chat in the fog. She's in his thrall as this tall, handsome man goes on about sailing to The Fortunate Isles.
She drops her fiancé and has an affair with the married Rennie. They frequently meet in a Chinese restaurant and go sailing. On one of their trips they are rammed in the fog by a freighter, Rennie is killed, and Begeddes survives -- beyond which medical discretion forbids me to go.
I don't know why the writers of this series sometimes seemed so sloppy. The city in which the story takes place -- fog, fog horns, Chinatown -- is obviously San Francisco and Belgeddes even makes a reference to Angels Island (presumably "Angel" Island). But why not invest a slender, half-hour drama like this with a sense of place? Name some streets. Introduce some local color. At least name the CITY. Have the loving couple stand at the foot of Telegraph Hill looking up at the phallic Coit Tower and have Michael Rennie observe off-handedly, "Did you know, my dear, that the name of Coit Tower has absolutely nothing to do with coitus?" Why not pluck the low-hanging fruit?