First, open the image in Photoshop that you want to apply the effect to. Next, in the layers palette right click on the image and make a duplicate copy. (note: all of the following work is done to the copy (or duplicate) layer) so, With the copy selected in the layers palette, apply the "find edges" filter by going to filter>stylize>find edges.
Original:
After the find edges filter:
Type Shift +ctrl +u to desaturate the image. Open the levels adjustment box with image>adjustments>levels and move the right hand carrot to the left to clean up the lines and remove some of the dark fuzzy look.
Back in the layers palette, apply a layer mask to the copy by clicking the appropriate icon at the bottom.
Make sure your foreground color is black and your background is white then hit G to bring up your gradient tool. With the layer copy still selected, drag the gradient from about the middle of the picture down about 2 inches (obviously this is a matter of preference, the farther you drag the gradient the less of the line drawing will show) when your done your picture should look similar to this:
Final:
