moved to the edge of their seats 
(ROOT (S (VP (VBD moved) (PP (IN to) (NP (NP (DT the) (NN edge)) (PP (IN of) (NP (PRP$ their) (NNS seats))))))))
(ROOT (S (VP (VBD ) (PP (IN ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (PRP$ ) (NNS ))))))))