shade,
silhouette, outline, dark, darkness, gloom, gloominess, dusk, dimness
antonym: light
ghost,
specter, spirit, wraith, apparition, phantom
constant
companion, alter ego, other self, double, doppelgänger
private
investigator, private eye (informal), private detective, gumshoe (US,
informal), sleuth, tail (informal), tracker
hint,
trace, suggestion, touch, shade, flicker
follower,
stalker, tail (informal), tracker, pursuer
follow,
tail (informal), trail, track, shade, stalk, observe, pursue, go after
darken,
eclipse, blot out, shade
antonym: brighten