Sentence:  A small lad, with a large head and faded yellow hair, <WSD>sidles</WSD> up to you, and says something about "Ing'n work," or "Cur'osities," or "Cam'ra 'bscura," or "Guide." You give some sharp, quick answer; the small boy collapses and vanishes. 
Meaning of the word marked with <WSD> tags:  "In the intransitive sense often followed by" '''(up)''': to (cause something to) advance in a coy, furtive, or unobtrusive manner.