A person lies alone in the quiet and lets their mind drift to a strange thought: "I could be anyone." The title, "Mutable," means changeable, and the poem plays with that idea. The speaker tries on possible selves the way you might try on clothes, without settling on one.
The images are odd and a little funny. A face "like a cake / or a clock" is something to be looked at, sliced, or read for the time. It suggests how a face can seem ordinary, even slightly absurd, once you stop taking it for granted. Then the tone softens: a "great heart ready to give" and a "body in peace" sound generous and calm.
The last line, "having money," lands flat and abrupt. It reads like another identity casually added to the list, and it may quietly undercut the tenderness before it. The mood is drowsy and wondering, with a hint of dry humor.