Sam’s adventure

It’s a very hot Texas night; 35ºC! Sam can’t sleep. He’s hot and he’s hungry. He goes to the kitchen. He cooks some fried bananas. But he forgets to turn off the gas. He leaves the kitchen and goes to the pool. His parents are asleep; they don’t know about his adventure.

He’s in the water-alone!

Mmm, It’s cool! Suddenly he gets cramp in his legs and he can’t swim. He looks at the house and it’s on fire. Sam’s parents are in there and he must help them. He is desperate.

The word “must”, in bold, in the text, indicate