if a roof or wall falls in, it falls to the ground
Example: And then after a while, she's saying, they started to fall in love.
if soldiers fall in, they move to stand in a straight line or other regular formation
Example: Her mind rebelled at the coincidence; the truth was beginning to fall in on her like a collapsing wall of hope, burying her alive.
if you fall in behind or beside someone, you start walking behind or beside them
Example: I understand now how an artist can fall in love with his own creations.
cave incollapsecrash insink