Then they left, they left for the mountain, they went on up.
( ( Then ( they ( ( left , ) ( they ( left ( for ( the mountain ) ) ) ) ) ) ) ( , ( they ( ( went ( on up ) ) . ) ) ) )
(ROOT (S (S (ADVP (RB Then)) (NP (PRP they)) (VP (VBD left) (, ,) (S (NP (PRP they)) (VP (VBN left) (PP (IN for) (NP (DT the) (NN mountain))))))) (, ,) (NP (PRP they)) (VP (VBD went) (ADVP (RB on) (RB up))) (. .)))
They decided to stay home. 
( They ( ( decided ( to ( stay home ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD decided) (S (VP (TO to) (VP (VB stay) (NP (NN home)))))) (. .)))