Yes Professor Sanchez seems sincere to Lola. There no particular book that stands out to you.

Edward sighed. This professor--presuming he was sincere--just wanted them to go with Larkin, and leave a trail, unnoticed by the man. Even though the man's intentions wouldn't be revealed until he got back to town anyway. Unless he WAS working with a death cult, in which case the professor not only wouldn't be of assistance, but apparently he wouldn't even have the resources to protect himself should Larkin get wind of his scheme at any point. "What a mess," he thought as he put a curled finger to his chin, wondering if he should have demanded partial payment upfront.

"You seem sincere, professor. But you still haven't told us why you think Larkin is merely in it for himself." The young man didn't mention the involvement of de Mendoza; no need to distract from Larkin's alleged greed with his potential alleged involvement with murderers.

"Thank you professor, but what I meant was, what are you going to do about Larkin and his henchman when we all reach the pyramid? Will you be coming alone or with people who can enforce your will to preserve the pyramid?" The british gentleman patiently presses on.

Professor Sanzhez looks expectantly at each of you "I ask for your assistance in quelling any thugs and to help preserve a part of history"  He then looks at the clock  "Rizo should have been back by now. I am sure she is lost looking at some artifact. Can I ask all of you to search for my errant student. I am sure the translation and summation of the Conquistador's account is finished. She must be in the storerooms downstairs."

If the party accepts the professor directs the party to the stairs that head down.

James is not quite ready to pledge himself to the professor's cause. The british gentleman was certainly not here in Peru with the intention of any grave robbing and he sympathized with the professors ideas, but there was still a bit too much he didn't know about all this to make such an commitment the professor asked for. "Certainly professor, we'll find your student for you." He says, putting out his cigarette and turning to leave without hesitation.

Perception to locate missing student: 26

Without a word, only a slight frown at not being quite satisfied with the response, Edward followed James towards the stairs. Once out of earshot, he quipped "Well, this expedition just gets stranger by the day, doesn't it?" The young man hoped the others' input might at least convince him he wasn't crazy, and that the situation was as actually bizarre as it appeared to him.

(( Perception Check for student: 17 ))

The party heads down to the basement level and sees a long dark hallway. None of the lights are on and the hallway is so dark that you cannot even see the end of the hallway. The only light is from the stairwell. There is a light switch nearby, but flicking it on and off does nothing.

You hear a strange wet gurgle and gasping noises from farther down the hallway. With your excellent perception Ed and Mr. Devereaux surmise its coming from a room on the left side 20 ft ahead though its too dark to make out any details.

If your wondering how dark it is then this image will help.

"Agreed." The britsh gentleman says as he turns his head briefly to face Edward, offering a small smile of reassurance, then returning his focus on finding the missing student. Something didn't feel quite right about her disappearance and that feeling only grew stronger as he realizes the lights in the basement are out of order. He hears the ominous wet gurgling and gasping sounds from ahead and is determined to investigate but looks around what he can see from the stairs, hoping to possibly spot a flashlight or other light source.

Perception as bonus action due to Eye for detail feature: 9 

You can see just the beginnings of the hallway and there is no door you can see yet. There is also no flashlights in sight, but you may find one if you travel further down the hallway.

"What is that sound?" asked Edward aloud, although in a low voice and to no one in particular. A ridiculously dark hallway--far too dark for doing any sort of research--and strange noises coming from the area where the missing student was supposed to be? The adventurer's intuition was causing him to think the worst.

He fingered the revolver on his hip, and checked for the weight of the darts and daggers hidden on his person; finding them all to still be present, he crept forward, going more slowly and more stealthily the further to the end of the hall he got.

(( Stealth Check: 13 ))

As Edward creeps along the hallway he smells cleaning solution. The kind used on floors nearby to the right. Feeling against the wall you find a door handle.

Do you open it?

Edward slowly, carefully, and as quietly as possible turns the door handle and pushes open the door.

(( Stealth Check: 12 ))

Ed discovers the janitor closet with an assortment of cleaning supplies. Feeling around you find the broom, mop, and a flashlight

Lola shivers. She hadn't thought about the danger of thugs attacking them on this adventure, only considered the positive possibilities!

She follows the others down the hall, feeling in her pocket for her goggles of night. She pulls them on over her eyes and can instantly see more easily in the gloom. 

Perception 14

Lola can see 3 doors on the left and 3 on the right  where Ed as at the first door on the right which is the cleaning closet. The sound was coming from 1 one of the rooms on the left.

Lola, shaking slightly and listening intently, reaches out to try the first door on the left. She takes a deep breath, her eyes wide behind the goggles, before she tries the handle. 

Grasping about the room, Ed sighed with relief as he felt the flashlight. The young man immediately took hold of it, and tried to turn it on.

The flashlight turns on the light from it is ruddy yellow, but it works.

Lola the first door on the left is locked

Seeing Edward turning a flashlight on ahead, James moves to follow him towards the weird wet sounds.

Perception: 16