Suddenly, Larry tosses and turns. This is the last phase of his struggle. Whether he lives or dies will be determined by his will to live. And deep inside Larry, he still can be called upon to be responsible, even though he doesn't understand much about what is going on.

Stephen had taken ill about the same time Larry had taken ill.  With him not being well, he is uncertain whether anyone else will take care of Stephen.  He can't assume anyone else will ---it is his responsibility.  He has to check on him.  If Stephen isn't okay, it is no one's fault but his own.