The poem is about a person escaping into their imagination on a dull rainy day at work in England. In the person's mind, they get on a plane and go to a more interesting place. The poem is, therefore, at first about dreaming of impulsively leaving one's dull routine for a better land. The speaker mentions taking only a credit card and a coat. The coat will be left on the plane. In other words, the speaker is leaving the ordinary world behind to seek freedom.
In this imagined new place, a "beautiful boy" serves the speaker a drink as she sits at a bar overlooking a harbor. Both the server and speaker are watching the sky over the water. They see the moon rise. The server asks if people could land on the moon. At this point the speaker describes the moon by using a simile and comparing it to an orange:
A moon like an orange drawn by a child.
The image of the moon looking an orange is the high point of the fantasy of escape. It symbolizes the speaker being at the peak point of imagination, living as a child might in a land where anything is possible. After this high point, the speaker realizes, however, that not everything is possible. She says, "No. Never." As soon as she says those words the moon, imagination's symbol, begins to sink into the sea:
You watch it peel itself into the sea.
She awakes and in is her ordinary life back in England—which doesn't seem so bad after all now.