Can I say,
(a) After a few minutes, Peter's mother returned home. He told his mother about/that his key was lost. She quickly opened the house, and let him go in the home together.
(b) When Peter's mother came back, he told his mother about losing the keys. Then they went in
their home together.
(c) When his mother returned back from work, Peter told her (that) / told her about what happened just now.
(d) Peter's mother (had) finally returned home. Peter told her (about) the story / the fact / the matter. His mother used her key to open the door and went in the house.