rester à (+infinitive) -- to have something left to do.
s'enfuir -- to flee.
Il ne vous reste qu'à vous enfuir. -- You have nothing left but to flee.

Since it is reflexive, you have vous ahead of it, between the à and the infinitive. 

avoir à + infinitive -- to have to....
Qu'est-ce que j'ai à perdre? -- What do I have to lose?

Hi Jill,

The text seems to be expressing:-

1) All you have to do is to run away. Written: "It remains only that you run away" the à seems unnecessary to me. 

2) What have I got to lose? Written: "What is it that I have to lose?" again the à seems to be unnecessary being followed by the infinitive perdre (to lose)

So, in conclusion, I'm inclined to agree with you.

Let's see what others may add?

Jim

thank you both for the clarification! that helps- nice to know that this site and the people on it are there for help with this process