pass as a watch in the night

Probably people. The Watch is probably another name for the local police force. Might even be a tour of duty on shipboard.

Just guessing.

In the days of sailing ships and wooden navies, the day was divided into seven watches. The first watch was from 8:00 p.m. until midnight. The mid-watch was from midnight until 4:00 a.m.; the morning watch was from 4:00 a.m. until 8:00 a.m.; the forenoon watch was from 8:00 a.m. until noon. The nautical day began at noon, when officers and midshipmen would come out onto the quarterdeck, a raised deck covering the back one third of the ship. There, they would take an instrument called a sextant and "shoot the sun," which meant they would observe the sun through the sextant until it had reached its highest point, and that would be set down as noon in the log book, the record kept of the activities aboard the ship. This was important because as you travel east or west, local noon changes. (I'm not going to attempt to give you a lesson in spherical trigonometry, mostly because i can't do spherical trig--but take my word for it, your relationship to the sun changes.)

That was followed by the afternoon watch, from Noon to 4:00 p.m. This was followed by the first dog watch, from 4:00 p.m. to 6:00 p.m., and the last dog watch from 6:00 p.m. to 8:00 p.m. Then you start all over again.

During a watch, an officer would be in charge, usually one of the lieutenants or the sailing master. There would be one or more midshipmen on duty, and a quartermaster to oversee the steering of the ship according to the captain's instructions. Half of the sailors, the enlisted men, would be on duty to handle the sails and the rigging, and one or more of them would be "sent aloft." meaning they would be sent up into the rigging on the masts to keep a lookout for anything unusual and for other ships. They, and those on deck, kept watch for anything of note. According to Vegetius, a writer on military matters in the late foruth century, the Romans kept watch in the night by dividing the night into four, three-hour tours of duty. At sea, with all the 24 hours of the day to cover, the day was divided into five watches of four hours and two watches of two hours (the dog watches).

The first watch, from 8:00 p.m. to midnight, and the mid-watch, from midnight to 4:00 a.m., were times when no specific tasks were scheduled. The men on watch had to stay on deck, but they had little or nothing to do, unless an emergency--the enemy or bad weather appeared--so many of them would find a corner where they would not roll around and take a nap.

The watches of the night were, therefore, a time of bleary, uneventful hours passing. They are often described in literature as being a time of sleepless contemplation, or of dreamy confusion.

So, in your expression, a watch in the night, it means a set period of time when people were employed to keep watch--on a sleeping city, on a sleeping military camp, and most of all, on a sleeping ship.

The phrase "as a watch in the night" appears in a limited number of situations these days: (a) Psalm 90, verse 4 of English translations of the Old Testament of the Christian Bible; (b) people asking what the phrase means.

A fairly clear explanation of the meaning was provided by Sir John Chardin (1643-1712):

"...as the people of the East have no clocks, the several parts of the day and of the night, which are eight in all, are given notice of. In the Indies, the parts of the night are made known as well by instruments of music in great cities, as by the rounds of the watchmen, who with cries, and small drums, give them notice that a fourth part of the night is passed. Now as these cries awaked those who had slept, all that quarter part of the night, it appeared to them but as a moment."