We see two contrast lovers here.. One Zheng Si - who murder his lover for his selfishness and another Yanzi - who is true to his love and go extra mile to safe guard her.
This is the start of SuMuZhe involvement of the stolen goods and was framed. While YanZhijing showed his true feelings when he wanted to protect DuanWu from taken into prison... love is always stronger when in danger.