Was written all over their faces - Idioms by The Free Dictionary
be written all over (one's) face (redirected from was written all over their faces)
be written all over (one's) face
Of one's emotions or inner thoughts, to be evident by one's facial expression. Jenny said she wasn't scared before we went into the haunted house, but terror was written all over her face. John said nothing, but his response was written all over his face.
be (or have something) written all over your face used to convey that the presence of a particular quality or feeling is clearly revealed by a person's expression. informal
be written all over somebody’s ˈface (of an emotion) be clearly seen on somebody’s face: You could see he was guilty; it was written all over his face.