Wei Ying (compsci major, bisexual, never been hiking before) hasn't stopped talking for more than two minutes at a time since they got in the minivan, and that's not changing now. 

"Haha, Jiang Cheng, you screamed like a girl just now!" He elbows his brother but misjudges in the dark, nearly making both of them lose their footing on the slippery bank. 

"Did not! That was you! And don't shove me, you're gonna knock both of us in the river, idiot!" 

"Is everyone alright?" Duy, the trip leader, calls out. 

"I'm fine."

Kristopher has stepped away from the group and is sweeping his light across the ground in broad strokes, looking as if he's trying to find something.

"So are we," Macy says. 

Ted, her boyfriend, nods in agreement. He's tucked up against her side, arm looped through hers. 

"I wish the darkness had lasted longer," Fever says, "That was too short even to see any stars." 

"That is inconsiderate," the quieter Asian guy tells Fever disapprovingly. His name is Lan Zhan, but the other hikers only know that because Wei Ying has said it (or yelled it) at least 50 times while constantly trying to get his attention.  "Someone could have been hurt."

Also, it was very startling. Lan Zhan dislikes being startled. 

Wei Ying bounces in Kristopher's direction. "Ah, did you drop something? Want me to help you look for it?" 

He smiles at Wei Ying, but absently.

"No I was just..." he trails off before finishing the sentence with a half-hearted, "seeing if there way anything strange."

Fever scowls at Lan Zhan.

"Don't be dramatic. People can be in the dark for like, one minute, without falling over." 

She looks away from him, clearly done with conversation.

"Alright!" Duy calls, "If everyone's alright, let's get back to. I want to make camp before it gets any darker."

"I don't think it can get any darker!"

Wei Ying can help set up camp! Hopefully his enthusiasm, friendliness, and willingness to learn will make up for the fact that he's never done this before and certainly not in the dark. 

Jiang Cheng will also help, a word which here means 'attempt to stop Wei Ying from doing anything particularly stupid'.

Lan Zhan is still recovering from the unpleasant shock of the lights failing. That was Not Supposed To Happen. Hiking usually has a minimum of unpleasant disruptions compared to most activities, and today it has let him down. 

Wei Ying is also disruptive, but the tasks of setting up a camp are familiar and he can do them in the dark. 

He counts heads—well, headlamps—to make sure everyone is where they're supposed to be, doing what they're supposed to be doing. There should be eight including him; he remembers thinking when they set out that it was an auspicious number. 

He can see eight people's headlamps. 

That is incorrect. There should only be seven, with his own making eight.

Something is Incorrect and this is deeply upsetting. (To anyone watching him, he appears as blank-faced as ever.) 

Elena and Duy manage the setting up of the camp, they're very good at giving clear directions to beginners. Anyone particularly good at reading people may notice there's something slightly forced about Duy's cheerfulness. 

Elena isn't even attempting to be cheerful, instead giving out firm directions in a slightly tight tone of voice.

Once the camp is set up and everyone is settling in, Elena and Duy disappear together into the trees.

Lan Zhan has not yet mentioned the extra light to anyone. He doesn't know most of these people very well, other than Wei Ying and, he supposes, Wei Ying's brother. He met Duy, Elena, and Kristopher when they did this last year, but he barely exchanged more than a handful of words with Kristopher, Duy and Elena are out of sight, and everyone else is new. 

The wilderness survival handbook he read cover-to-cover in preparation for last year's hike, and reread before this one, did not have any instructions for this scenario. He is unsure what to do, and he can't ask Duy (as the nearest thing to an authority figure in the vicinity) until he comes back. 

He hovers uncertainly near Wei Ying and his brother, the two people in the camp he is the most confident were definitely here this whole time. 

Wei Ying would, if he knew, be delighted to learn that Lan Zhan considers him inimitable. 

"Lan Zhan!! Lan Zhan, do you think there'll be fireflies tonight? I wanna see fireflies! Did you see any last year?" 

"Mn." (No.)

"I bet you weren't looking in the right place. Fireflies like big open fields."

"Mn." (Yes.) He knew that. He's irrationally annoyed that she's right. Knowing that it's irrational doesn't make it less annoying.