Stevenson begins with the most ordinary comparison he could find: the moon has "a face like the clock in the hall." Nothing here is silver or mysterious. The moon is a household object, round, pale and watchful, hanging over the evening the way a clock does. A clock also tells you when it is time for bed, and the poem goes on to make that its quiet purpose.
Its central idea is that the world works in two shifts. By night the moon "shines on thieves on the garden wall, / On streets and fields and harbour quays," and the list stretches outward from the garden to the whole neighbourhood, even down to the water. In the second stanza the night creatures arrive: "the squalling cat and the squeaking mouse, / The howling dog by the door of the house." Then the third stanza turns on a single "But" and brings in the day's creatures, who "cuddle to sleep to be out of her way." The poem argues, gently, that darkness is not empty or frightening. It is simply someone else's working hours.
The sound of the poem helps make it feel safe. Each line has four strong beats with a skipping, galloping rhythm: "The MOON has a FACE like the CLOCK in the HALL." The lines are paired in rhyming couplets (hall/wall, mouse/house, day/way), which snap shut like a nursery rhyme. That steadiness is soothing, and it suits a poem that may well be meant to send a listener off to sleep, though the text only suggests this. The second stanza adds noise to the rhythm. "Squalling," "squeaking" and "howling" are harsh, vivid sounds, yet they sit inside the smooth couplets, so the racket of the night comes out sounding cheerful.
Stevenson also has a talent for small, tilted details. "The bat that lies in bed at noon" is funny because it borrows the language of a child's bedtime for an animal, and it neatly reverses the human day. The bat is not hanging or roosting; it is "in bed," just in the wrong part of the day. The thieves in line two add a hint of mischief and risk, but they are placed on a garden wall beside everything else, with no more menace than the cat. Even the "birdies asleep in the forks of the trees" are described in a diminutive, tender way. Judging by that word, the speaker is an adult talking to a small child, and the whole poem has the tone of someone lowering their voice at the end of the day.
The moon herself is the most interesting presence. She is "she," and in the last stanza the day's creatures keep "out of her way," as if she were a grand lady sweeping through a room and everyone had to step aside. There is a touch of authority in that, even a little awe. Yet the verb chosen for the sleepers is "cuddle," which is soft and domestic. The moon commands, but nobody seems afraid of her.
The final couplet brings the poem back around: "flowers and children close their eyes / Till up in the morning the sun shall arise." Putting children and flowers together is the poem's most affecting move. It places the child inside nature's pattern, as one more living thing that rests when its turn is over. The slightly formal "shall arise" gives the sun a stately entrance, a counterweight to the moon's, so that the poem ends with a promise that the cycle will turn again. Sleep becomes something to look forward to, because morning is guaranteed.
What makes the poem significant is how much it achieves with so little. It takes something huge and distant and makes it as familiar as the hall clock. It acknowledges that night has noise, animals and even thieves, then arranges them so that the effect is comfort rather than fear. Underneath the simple rhymes lies careful structure: a stanza of sights, a stanza of sounds, and a stanza of sleep. A child hearing it would simply feel that the dark was looked after, which may be the real achievement of the poem.