Negative Minus — Patricia Fanthorpe

A space liner is a brilliantly designed machine. It is not the kind of thing that disappears without good reason. The Q 97 bound for Alpha Centauri vanished with disquieting suddenness. Stelgen and his crew of expert investigators went in pursuit...and also vanished!
On the other side of Infinity they found a nightmare galaxy where things of incalculable power plotted cosmic evil. Stelgen argued that somewhere, somehow, there had to be an answer to the apparent invincibility of these unbelievably deadly aliens. His problem was to find the answer and get it back to his own people. Trouble was, that someone from the Q 97 was working against him...
When an answer finally presented itself it was so beautifully simple that it needed a genius to see it, and whatever his other qualities Stelgen was not a genius.