Traveling backward in time, Don Miguel had to undo the errors and interruptions of other time-interlopers. Even the most insignificant nudging of the past could entirely alter the present! And he suspected that a maniacal genius crazed with a desire for nationalist vindication had plotted to alter the victorious outcome of the Spanish Armada of 1588 - thus changing recorded history and perhaps even imperiling the Imperial Spanish Empire of 1988!
If Don Miguel did not successfully intercede, when he came back to the present he might find a different world...a different time...a time in which he probably didn't even exist!
Although termed a novel it is really a group of three novelettes previously published under the titles:
Spoil of Yesterday (1969 revised/expanded edition)
The Word Not Written (1969 revised/expanded edition)
The Fullness of Time (1969 revised/expanded edition)