The second half of this movie seems to be largely inspired by "Eye of the Needle" which I had watched twenty years back. It starred Donald Sutherland. "Eye of the Needle" has the backdrop of World War II. A German spy gets marooned on a desolate British island colony, probably Gibraltar. He falls in love with a woman who stays on the island with her crippled husband and their son. She too falls for the hero. When she learns about the hero being a spy she mercilessly shoots him. The tag-line of the movie ran like 'it is easy to love an enemy but difficult to kill a lover' (not verbatim). Replace the island by Kashmir made inaccessible in winter. Replace the German spy by lost husband terrorist. Crippled husband by alcoholic father. Presto, you get "Fanaa".

The story writer (who won a Filmfare award for this movie!) owes us an explanation.