The plot basics of the eight-part “Unbelievable” series are routine: young woman is raped in Washington state and police dismiss the event, then three years later in Colorado, two determined female detectives set after the rapist following a similar rape. This could have ended up heavy-handed, with wincing scenes, or it could have been plodding police procedural fodder, but with a fine team of writers, excellent direction, and stellar acting, “Unbelievable” was one of last year’s best screen outings. Kaitlyn Dever is stunningly vulnerable yet inwardly sturdy as the first rape victim, Merritt Wever is so, so authentic as the relentless, humane younger detective, and Toni Collette inhabits the older, swaggering, crusader of a detective. Of particular note is that two of the three central characters, the avengers for goodness sakes, don’t even hit the stage until Episode 2. Such is the confidence of this series! “Unbelievable” surefootedly, with a growing sense of menace and desperation, seesaws between the nitty-gritty, two-steps-forward-one-step-back police work and the victim’s travails. The climax resists sensationalism and offers hope. Do yourself a favor and take your time (no binging) with this important series.