Complex sentence: Gersen spends some time examining the "Cosmopolis" files for any material relating to Treesong, and is on the point of giving up when he discovers a photograph, apparently of a formal dinner, bearing the words "H A Treesong is here".
Split into simpler sentences: Gersen spends some time examining the "Cosmopolis" files for any material relating to Treesong. He is on the point of giving up when he discovers a photograph, apparently of a formal dinner, bearing the words "H A Treesong is here".