The fourth season of Netflix’s ‘Stranger Things’ is brooding and dark, mirroring the moodiness often associated with humans teetering on the edge of adulthood — otherwise known as teenagers. The murder dial is turned way up. But truth be told, the kids of Hawkins, Indiana, have always punched above their emotional weights. That tends to happen when you risk your life to save the world from salivating monsters and Soviets. Still, this iteration of the hit nostalgia roller coaster leans heavier on the way down than on the hopeful ride to the top.