Lensman from Rigel

Oct. 1983 Bantam mass market paperback, 3rd printing. David A. Kyle (A Pictorial History of Science Fiction). Following the events of The Dragon Lensman (the first book in the "Second Stage Lensman" Trilogy), Tregonsee is made violently aware of a deadly new threat to the forces of Civilization when he is targeted for assassination by an unknown power capable of precisely controlling hyperspatial tubes -- portals that fold the fabric of space-time itself to make possible instantaneous, untraceable transportation anywhere in the universe.