grabs you in the dark and shakes you vigorously for its duration . 
(ROOT (S (VP (VBZ grabs) (NP (PRP you)) (PP (IN in) (NP (DT the) (NN dark)))) (CC and) (VP (VBZ shakes) (NP (PRP you)) (ADVP (RB vigorously)) (PP (IN for) (NP (PRP$ its) (NN duration)))) (. .)))
(ROOT (S (VP (VBZ ) (NP (PRP )) (PP (IN ) (NP (DT ) (NN )))) (CC ) (VP (VBZ ) (NP (PRP )) (ADVP (RB )) (PP (IN ) (NP (PRP$ ) (NN )))) (. )))