Before Season 5
Paige, died tragically at the age of only 3 years old, in a car accident, along with her mother Lila, after the latter decided to take her out for ice cream . It is revealed that Mike Delfino was the driver who crashed into Dave's car killing his family. Later, we find out that it was actually, Susan Delfino who was driving the car and because she couldn't find her license, Mike Delfino took the blame for his wife.
Dave tells Edie Britt-Williams (his new wife) about the tragic death of his family. But Edie later finds out Dave's plan to kill Katherine Mayfair, Mike Delfino's girlfriend as a way of getting his revenge for the deaths of his wife and daughter. Edie sees a picture of Paige in an old newspaper. Which then leads to her death after telling Dave that she knew about his past and his plan. She runs away after Dave almost strangles her and crashes into an electrical post before stepping outside and into a puddle. She receives an electrical current, killing her.
Paige is constantly appearing in episodes along with her mother Lila, as a ghost. It is because of Paige Dash that Dave does not kill M.J. as he sees her sitting in M.J.'s seat and tells M.J. to get out of the car before it is hit by Mike Delfino.
If Paige was still alive, she would have been the same age as M.J.