Possible Clues:

• Plain father's back with mother
• Evident, seeming
• It is obvious that father came back before mother?
• When Father returned by himself the rift was obvious
• Father must go back by himself: that's obvious
• Conspicuous, Guardian lying under a piano
• Sounds as if the visible air should succeed
• Quite obvious
• It's clear dad's back with mum?
• Pane part may be quite obvious