it establishes its ominous mood and tension swiftly , and if the suspense never rises to a higher level , it is nevertheless maintained throughout 
(ROOT (S (S (NP (PRP it)) (VP (VBZ establishes) (NP (PRP$ its) (JJ ominous) (NN mood) (CC and) (NN tension)) (ADVP (RB swiftly)))) (, ,) (CC and) (S (SBAR (IN if) (S (NP (DT the) (NN suspense)) (ADVP (RB never)) (VP (VBZ rises) (PP (IN to) (NP (DT a) (JJR higher) (NN level)))))) (, ,) (NP (PRP it)) (VP (VBZ is) (ADVP (RB nevertheless)) (VP (VBN maintained) (PP (IN throughout)))))))
(ROOT (S (S (NP (PRP )) (VP (VBZ ) (NP (PRP$ ) (JJ ) (NN ) (CC ) (NN )) (ADVP (RB )))) (, ) (CC ) (S (SBAR (IN ) (S (NP (DT ) (NN )) (ADVP (RB )) (VP (VBZ ) (PP (IN ) (NP (DT ) (JJR ) (NN )))))) (, ) (NP (PRP )) (VP (VBZ ) (ADVP (RB )) (VP (VBN ) (PP (IN )))))))