Ace (#01043; 1st edition) 1969 paperback. Cover by Sergio Leone, 255 pages. Condition is VG+: tight and square with flat spine; very mild uniform age tanning; light overall wear. No stamps, marks or writing.

All 4 of the "Agent of T. E. R. R. A." series appeared as written by "Larry Maddock." (Real name is Jack Own Jardine.) Hannibal Fortune was one of top half-dozen operatives of the Galactic Federation's Temporal Entropy Restructure and Repair Agency (T.E.R.R.A.) In the chess-game between the Federation and EMPIRE, he was the equivalent of a bishop or rook, and Licensed to Tamper in time. His partner was a small 15 pound symbiote named Webley who could change shape at will. [There were 3 stories featuring Webley in New Worlds in 1960 (as by Larry Maddock), but he (it?) was partnered with someone else, and no time travel was involved.]

EMPIRE, the evil force of time-criminals, never interfered with history unless they had a good reason. This time, EMPIRE was altering Earth's time-line to make Rome lose the Second Punic War, because this tampering was certain to lure T.E.R.R.A.'s top agent, Hannibal Fortune. EMPIRE wanted him dead, so they trapped him in otherwhen, in a time-period he had already been in - thus violating the deadly Rule of Doubletime: no man can exist twice at the same time. It meant that Hannibal Fortune simply would not exist at all…