what happened at the end?

http://en.wikipedia.org/wiki/Frank_Gilbreth

I would normally suggest watching it, as I adore this movie, bt it may be a little hard to come by a copy :)

Short version is that Frank dies, and his wife carries on his work.

Slightly longer version:
Spoilers:

Frank Sr. dies of a heart attack before leaving to speak at two European conferences; Lillie, after running the idea past the kids, takes his place at the conferences and continues his work. All of which neatly leaves the window open for the sequel.