tiān hēi qián / duìwǔ / bìxū / chuānguò / shāngǔ / fǒuzé / hěn kěnéng / bèi / zhuībīng / gǎnshàng

天黑前，队伍必须穿过山谷，否则很可能被追兵赶上。

The group must cross the valley before dark, or the pursuing soldiers may catch up with them.