It took Zhang Tie only a bit more than 6 hours from Sunshineprospect River to Dragon Emperor City.
Zhang Tie returned to Dragon Emperor City at around 4 pm. It was still sunny in Dragon Emperor City just like usually. During the past 4 days, nobody across Dragon Emperor City had discovered that Dragon Emperor was not in the Forbidden City; instead, he had left Dragon Emperor City and 'made a big harvest'...
Just like he left there, Zhang Tie returned to Forbidden City secretly through the secret tunnel outside Dragon Emperor City before entering his own backroom for cultivation beneath Jiaotai Palace.
As immortal generals always entered secluded cultivation for a long time, the short period of 4 days was not a big deal for immoral generals. The backroom was as same as before. Leng Manxue had not contacted Zhang Tie; perhaps she thought that Zhang Tie was still inside there.
