Какой инфинитив мы используем после must / mustn't with или without​

A person will never find an absolutely disinterested friend in this selfish world, a friend who will never leave you in trouble, which will never prove ungrateful and treacherous. A dog belonging to a person will always remain with a man, whether he is prosperous or poor, healthy or sick. The dog will always be next to the owner, whether it's terrible cold, piercing wind and heavy snowfall. A dog licks your hands, although you can not repay it; she licked wounds and sores, facing the brutality of this world. The dog guards the poor man's sleep as if he were a prince. All friends leave it, but the dog remains. When the wealth disappears and the reputation is shattered, the dog continues to love the owner passionately - this love is like the sun floating in the sky. You can tell a dog anything you like to a dog, she will not tell anyone, she will understand, this is the only animal that loves you more than yourself. So definitely a dog is a friend of a person. But I'm not sure whether a person can be considered a friend of a dog, people in our time are too cruel.

Sam and Kate were inside the temple. It was dark there. Sam lit a fire.
Beano returned to the camp and found Professor Wallace. The professor saw a smoke signal. She ran to the forest and rescued them from the old temple. They found some old paintings on the wall of the temple. The first one was a picture of a beautiful girl. The girl in the picture had the orchid in her hand and she gave it to the young prince.
Then they found a picture of a rock. It looked like an eagle.
Now they are outside the temple and Beano is with Sam. But Joseph Alexander isn't with them. They are a long way from their camp now. They are going to find the orchid and they will go to Eagle Rock. Who will find the orchid?