On your thesis statement, keep it broad. So you would say in your introduction, that both writers portray time as a beast in which the speakers must escape. Then in your essay, you would go on to examine how they do this looking at their use of e.g. physical descriptions, how they create an atmosphere of fear, differing depictions of the 'beast' , how they create a sense of flight and escape etc etc. As you discuss each of these ideas that support your thesis, you draw evidence from the text that relates to language, style and structure, and compare and contrast your selected texts. Does that make sense?