Here, Burt Franklin Jenness is waxing nostalgic for his days in the navy now that he's freshly mustered out on shore. The "Mystery" is of course the culture shock of re-entry into civilian life:

From OCEAN HAUNTS, edited by Burt Franklin Jenness,
Empire Publishing Co., New York, US, © 1934, pp. 57-58.

THE MYSTERY

I'm back on my old job again; the boss has raised my pay;
I've donned "civilians," and I've put my uniform away;
The folks are proud because their son has done his bit at sea,
And everybody 'round the house is happy — except me.
There's something I don't understand, about this coming home;
For when I should be most content, my thoughts begin to roam;
And when I light my cigarette, I seem to see the gang
Up for'rd on the fo'c's'le, and I hear the songs they sang.
When I'm awakened by a voice, I think it's not for me,
And I turn over for a nap, and wait for reveille;
And 'round the steaming coffee every morning, now, there clings
The memories of mess time, and all the joy it brings
When a fellow comes off morning watch, with not a bite since four,
And cold and drenched — and his relief a half hour late, or more.
The wind that howls around the house, but brings delight to me,
For I hear the creak of gear, and racing screws at sea;
The sleet which cut my face today, as I walked into town,
I fought, in fancy, on the bridge, where I paced up and down;
There's something strange about the way I dream, now, on the job,
And stranger still, that I should long to be once more, a gob.

Notes

"Gob" is navy slang for a sailor.

Cheerily,
Charley Noble