how to make two other points to make a plane?

I'm trying to use function now.

[I,check]=plane_line_intersect(n,V0,P0,P1)
%       n: normal vector of the Plane 
%       V0: any point that belong   s to the Plane 
%       P0: end point 1 of the segment P0P1
%       P1:  end point 2 of the segment P0P1

To get the normal vector, I need 3 points on the plane.

but I have only one point(4,5,7), so I made two arbitrary points. but it seems to have trouble in z value.

it only returns x and y value. all z value is zero

Here is my code.

intersection_point = [];
for i = 1:length(mean_trajectory_double)
    O = [mean_trajectory_double(i,1),mean_trajectory_double(i,2),mean_trajectory_double(i,3)];
    P = [mean_trajectory_double(i,1)+1,mean_trajectory_double(i,2)+1,mean_trajectory_double(i,3)-1000];
    Q = [mean_trajectory_double(i,1)+2,mean_trajectory_double(i,2)+2,mean_trajectory_double(i,3)+1000];
    OP = Q-O;
    OQ = P-O;
    normalvector = cross(OP,OQ);
    for j = 1:length(RKSI_Arr_33R)
        for k = 1:length(RKSI_Arr_33R(j).Latitude)-1
            [I,check]=plane_line_intersect([normalvector(1) normalvector(2) normalvector(3)]...
                ,[mean_trajectory_double(i,1) mean_trajectory_double(i,2) mean_trajectory_double(i,3)]...
                ,[RKSI_Arr_33R(j).Longitude(k) RKSI_Arr_33R(j).Latitude(k)  RKSI_Arr_33R(j).BAlt(k)]...
                ,[RKSI_Arr_33R(j).Longitude(k+1) RKSI_Arr_33R(j).Latitude(k+1)  RKSI_Arr_33R(j).BAlt(k+1)]);
        end
    end
    intersection_point = [intersection_point;I];
end

O is the point I know already and P, Q is what i made.

mean_trajectory_double(i,1) is longitude

mean_trajectory_double(i,2) is latitude

mean_trajectory_double(i,3) is altitude

I changed the P and Q's altitude several time, but it always returend zero.