The Judas Strain extract

Gray’s fingers refused to move, clamped around the phone.
It vibrated and rang again.
He could almost feel the fury emanating out of it, an anger ready to be unleashed against his mother and father. He wanted desperately to answer it: to scream, to beg, to curse, to bargain.
But he had no leverage
Not yet.
“Nasser must still be in the midflight,” Gray finally mumbled to the phone.
“Due to touch down in five hours,” Seichan agreed.
Gray let a coolness wash through him, but his fingers tightened harder. “Up in the air, he’ll hesitate to make any major decisions. He’ll wait until his feet are on the ground before making a final assessment.”
“And if he hasn’t heard from you by then…”
Gray couldn’t say the words. He only nodded his confirmation. Nasser would kill his parents. He wouldn’t wait any longer than that. He’d punish Gray and move on to a new strategy.
Five hours
“We’ll need more than the second key we found here,” he said. “More than even the third key.We need to have solved the obelisk's riddle."

1. How does the first paragraph set the mood of the extract?

2.How does the obelisk riddle link to every comflict in this extract? Explain and quote evidence.