Alexander Blish was the security chief at Tomloy's the new nuclear-physics research centre. They were doing things in the plant that had never been done before. They were tapping power sources so terrible that their ultimate conclusion could be heaven on earth or a hell of destruction. Armageddon might be just around the dangerous corner which humanity called tomorrow.

Blish had problems. There were alien forces to consider. There were human traitors who were prepared to sell out the Empire if the price was right. The price could be as high as planetary control.

Wilkie Gordon was Alexander's second problem. Wilkie was an outworlder with strange wild talents. He could be an invaluable ally or a deadly enemy. Blish had to decide and decide at once. If he made the wrong choice a world might die. If he made the right choice there was just a chance that Gordon could detect the aliens and renegades before they reached the J-Pile ....

Rudolf Mallory was one of the many pathetic pieces of human flotsam on the tide of 20th-century neurosis. He was a man who had reached the end of his rope, death seemed pleasant by comparison.... He tried to take the easy way out, but something went wrong. Unknown to Mallory other men had problems too. Separated by vast distances of time and space, Rumal, citizen of an advanced humanoid society, with a strangely different technology had also decided to end it all....

Time and Space are almost perfect but rare warps and blemishes do exist in the continuum. They can produce peculiar results.

The Englishman from 1963 suddenly found himself on the other side of the galaxy. Rumal found himself in England. They had been unable to solve their own problems - could they solve each other's?