an engrossing story about a horrifying historical event and the elements which contributed to it 
(ROOT (NP (NP (DT an) (JJ engrossing) (NN story)) (PP (IN about) (NP (NP (DT a) (JJ horrifying) (JJ historical) (NN event)) (CC and) (NP (NP (DT the) (NNS elements)) (SBAR (WHNP (WDT which)) (S (VP (VBD contributed) (PP (IN to) (NP (PRP it)))))))))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (PP (IN ) (NP (NP (DT ) (JJ ) (JJ ) (NN )) (CC ) (NP (NP (DT ) (NNS )) (SBAR (WHNP (WDT )) (S (VP (VBD ) (PP (IN ) (NP (PRP )))))))))))