The bus arrives before the city wakes up. That's exactly the point.
Lai Chau city at 5am is quiet in a way Sa Pa never is. The market vendors are setting up. The streets smell like woodsmoke and "Pho". The sleeper bus from Hanoi pulls in and the day begins before most tourists in the northwest have had breakfast.
Day 1 runs south through the valley. PuSamCap Cave is a limestone cave system that sits an hour from Lai Châu city — galleries of stalactites, an underground stream, and almost no other visitors. From there, Lao Chai 1: a H'Mong village where the blacksmith forge is still the centre of the community. Lunch in the village. Then Tac Tinh Waterfall — a waterfall in a narrow gorge where the water is cold and the afternoon light comes through the trees at an angle. By sunset, you're at Si Thau Chai, a Dao village on the ridge, watching the light leave the valley from the homestay terrace.
Day 2 goes deep. The drive to the Nam Luc waterfall trailhead takes three hours and ends at a clearing at 430m. From there, the forest closes in. The trek gains 470 metres through primary jungle to the waterfall base, then pushes to the summit at 900m. The water is loud, the pool is cold, and there is no one else here. The day ends at Linh Ung Temple — a Buddhist monastery at 1,250m on the ridge above the city. The monks built it for prayer. The view is consequence, not intention.