a plot that crawls along at a snail 's pace 
(ROOT (NP (NP (DT a) (NN plot)) (SBAR (WHNP (WDT that)) (S (VP (VBZ crawls) (PRT (RB along)) (PP (IN at) (NP (NP (DT a) (NN snail) (POS 's)) (NN pace))))))))
(ROOT (NP (NP (DT ) (NN )) (SBAR (WHNP (WDT )) (S (VP (VBZ ) (PRT (RB )) (PP (IN ) (NP (NP (DT ) (NN ) (POS )) (NN ))))))))