Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Look Over Your Shoulder
Because all of the characters in Splendors and Glooms are pretty street-savvy and have learned some tough life lessons (even if they're just kids), the overall tone isn't too naive or trusting. For the most part, the tone of the story is cautious and careful, especially when the characters are trying to figure out the strange things happening in their lives.
For example, Lizzie Rose definitely gets pensive and concerned when she learns that Grisini has been questioned about the disappearance of children in the past. She doesn't know whether or not she should tell the police:
"Grisini would kill us," Parsefall said desperately. He dug his fingernails into her hand. "If we peached on him, he'd kill us. You don't know 'im the way I do." He heard his voice rise and lowered it again. "Promise me you won't go to the coppers."
Lizzie Rose gave a little shiver. She wasn't promising anything. (10.58-59)
But, it's not just caution that permeates the story. The characters are also super determined and hardy. They overcome all kinds of adversity, glancing over their shoulders before charging onward anyway.