Point of Intersection - Straight line and Curve

I have real data points in which one of them forms a straight line and
the other is a curve(not a simple curve, but more jagged). When I
graph the two, I notice there is a point of intersection between the
straight line and the curve. This point of intersection is not one of
the "data" points that I have plotted. Is there a way to determine the
point of intersection of the line and the curve? Any help would be