No, they didn't, no, just that one.
( No ( , ( they ( ( ( ( did n't ) ( , ( no , ) ) ) ( just ( that one ) ) ) . ) ) ) )
(ROOT (S (INTJ (UH No)) (, ,) (NP (PRP they)) (VP (VBD did) (RB n't) (PRN (, ,) (INTJ (UH no)) (, ,)) (PP (RB just) (NP (DT that) (NN one)))) (. .)))
Only one person was involved. 
( ( Only ( one person ) ) ( ( was involved ) . ) )
(ROOT (S (NP (RB Only) (CD one) (NN person)) (VP (VBD was) (VP (VBN involved))) (. .)))