Human Nature and The Family of Blood episodes start off with Martha and The Doctor running. The audience is led to believe they are running from a really powerful enemy that left the Doctor no choice but to go into hiding. He becomes human for the two-parter and it's only revealed at the very end that he only ran to show the Family mercy. He originally planned to let them live out their lives but since they kept pursuing him, he decided to deal with them in some pretty cruelly if you ask me. The two episodes do a very good job at contrasting a very human Doctor and the cold Timelord he is.