After reading The Field Book of Ponds and Streams over and over again Annie desperately wants to get her hands on a microscope. She thinks that everyone needs one, not just detectives at the FBI and Scotland Yard. Although she normally has to save her pennies carefully if she wants to buy something for herself, she's fortunate with regards to the microscope as her parents buy her one for Christmas.

Annie is understandably elated and loses no time in trying out her shiny new toy. All through that winter she carefully examines all kinds of weird and wonderful things through the microscope, including even the iridescent crystals in her urine. Now this is all very exciting, but what Annie really wants to do with the microscope is to look at all the fascinating wildlife she's been reading about such as the amoeba, a single-cell organism that has the ability to alter its shape. At first, Annie looks for an amoeba in the hay infusion, but can't find him. However, when she examines some puddle water she'd collected from Frick Park, at long last she finds what she's been looking for, all blobby and grainy, just as he'd appeared in the picture in The Field Book of Ponds and Streams.