Snake in the Garden

I opened the book at random (pp. 126-127):

The triumph of Tolly and Ping brought Mrs. Oldknow out to the gate. They seized her by the arm, one on each side, and hurried her laughing and breathless along the riverbank. Ultimately they saw the egg go over the weir, followed by the whole troubled mass of live water.

"The two adders in my armchair left as suddenly as if someone had whistled for them," the old lady said. "I went across the lawn to see where you were in the orchard, but all I could see was half of Tolly hanging on the pear tree. Of course, Melanie was on the road just there, looking very inquisitive. She seems to prowl round the outside of the place like a rejected lover."

"Heavens! We forgot the glass."

They had hardly dared to hope so, but it was still there when they reached the tree. If Melanie had meant to take it, she must have been distracted by other things. Those who cast spells must surely have a sense of near panic when their power goes wrong.

The glass was restored to its place in the attic. As the boys went up and down through the house, though they were too polite to look through the window that gave from the Knights' Hall into the spare room, they were aware of Mr. Pope's working there and longed to ask him how he was getting on and if there had been any snakes in his ground-floor bedroom. They were glad they had found the book before Melanie had sent the snakes. Otherwise, the roof space might have been full of them.

***
"If there's a snake in your garden sooner or later it will wind up in your house."