Complex sentence: At the track, Dink happens across a woman who, unknown to either of them, is actually his mother Linda, now re-married to Tony, a wealthy man who owns one of the other horses in the race.
Split into simpler sentences: At the track, Dink happens across a woman who, unknown to either of them, is actually his mother Linda. She is now remarried to Tony, a wealthy man who owns one of the other horses in the race.