For this relief much thanks: ’tis bitter cold,
And I am sick at heart.

– William Shakespeare

Hamlet, Act 1, Scene 1. Francisco complains to Barnardo, during a changing of guard between the two. This reveals that he is anxious or worried. And it speaks to the theme of death, disease and corruption in Denmark’s royal household. Francisco’s "sick at heart" comment foreshadows the appearance of the Ghost later in the scene.