I felt this episode was one of the better written. What starts off as a child's search for her biological mother suddenly turns into a family crisis when her quest causes the revelation of some terrible secrets.
This episode treated the family crisis well. The otherwise loving and caring mother finds herself exposed (accidentally) by her own daughter, and she is forced to confess the deceptions she restorted to to regain her illigitimate child. The father responds with understandable anger.
The ending seemed a bit abrupt. The father had literally stormed out of the house because his wife had been deceiving him during their entire marriage. Considering the depth of the wife's guilt, Mark's abortion comment seemed a rather weak reason for the father to go through such a drastic change in attitude.
This episode is also a chance to see some early work by a young Shannen Doherty. Also, this is one of the first episodes I recall where Michael Landon's role is reduced to a cameo.