One of many things that gets lost in adaptation is the extended courtship between Marius & Cosette (usually condensed to love at first sight). They pass each other in the park on a daily basis w/o paying much attention to each other, until she hits puberty & they start stealing glances at each other, trying to keep Valjean from noticing. She’s a lot better at that part than he is, though, which gets funny at times.
#LesMiserables
It does get creepy later on when Marius starts, well, creeping around her garden at night.
But at this point, it’s funny watching Marius hide behind trees so he & Cosette can make eyes at each other w/o Valjean seeing, make a fool over himself with the handkerchief he thinks she dropped (it was actually Valjean’s, so she can’t understand why he’s so fascinated by it), etc.
And when Valjean gets suspicious, and sets traps? Marius blunders into every single one.