This is a very cute cartoon, but not an especially interesting short on its own merits. The chief point of interest here is as the very first cartoon which Chuck Jones directed. As I will mention some details, there will be mild spoilers:

The basic premise of this short is that the regular night watchman, a full-grown cat, is sick and can't make his rounds and so the task falls to his young son. To say that the mice are less than concerned about the new night watchman would be an understatement. They're bigger, meaner and tougher than the little cat and bully him mercilessly.

This turn of events means that they have pretty much got free run of the kitchen for most of the short. There are a few cute food-related sight gags, but the short is a bit flatter and less energetic than you would expect, though, to be fair, if you look at it without comparing it to later work by Jones, it comes off looking a good deal better.

The ending is all rather predictable, though fun to watch for the most part. This isn't a bad short, it just pales in comparison to the work which would come later, though it does make clear that Jones was interested in the cute and sentimental from the beginning. This was probably the genesis of the Sniffles shorts done a bit later.

This short is available on the Looney Tunes Golden Collection, Volume 4 and is worth a look. The Collection, as with the previous three volumes, is most highly recommended.