When Mr. Hastings and Mr. Lawrence came in yesterday evening, they found your mistress busy writing letters. 
( ( When ( ( Mr. ( Hastings ( and ( Mr. Lawrence ) ) ) ) ( ( came ( in yesterday ) ) evening ) ) ) ( , ( they ( ( found ( ( your mistress ) ( busy ( writing letters ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNP Mr.) (NNP Hastings) (CC and) (NNP Mr.) (NNP Lawrence)) (VP (VBD came) (PP (IN in) (NP (RB yesterday))) (NP (NN evening))))) (, ,) (NP (PRP they)) (VP (VBD found) (S (NP (PRP$ your) (NN mistress)) (ADJP (JJ busy)) (S (VP (VBG writing) (NP (NNS letters)))))) (. .)))
Your mistress wrote letters last night.
( ( Your mistress ) ( ( ( wrote letters ) ( last night ) ) . ) )
(ROOT (S (NP (PRP$ Your) (NN mistress)) (VP (VBD wrote) (NP (NNS letters)) (NP (JJ last) (NN night))) (. .)))