Reader Suspense And Donnan's Moment Of Realization

Poul Anderson, After Doomsday.

"'I'll buck for sticking around myself,' Donnan agreed, 'though I got a kind of different reason. You see - Hullo, there's the end of our stroll.'"
-CHAPTER THREE, p. 35.

"Sticking around" means staying within the local civilization-cluster, which covers a lot of sky, but we are not told his reason for a while. He wants to "'...produce a sensation...'" so that:

"'...eventually the other human ships will hear the yarn and understand.'"
-CHAPTER FIVE, p. 61.

"Despite his wide experience, Ramri could still get number systems confused."
-CHAPTER SIX, p. 65.

Because of their different numbers of fingers, different races have number systems with different bases like six, ten or twelve. This will be part of the clue as to who murdered Earth. In fact, here is the earlier part of the clue, a conversion table found inside a missile patrolling Earth:

"ABCDEF
"MNOPQ MR
"BA:PM
"ABIJ:MOQMP
"JEHC:NMQPPO"
-CHAPTER FOUR, p. 48.

Two sets of alien symbols have been represented by Roman letters. Recognizable Kandemirian numerals have been represented by A through L whereas a different set of symbols has been rendered by M through R. If the M-R symbols are numbers to base 6, then they might give us:

R=0
M=1
N=2
O=3
P=4
Q=5
MR=6 (rendered as the equivalent of "10" to base 6)

The six-fingered Monwaingi count in sixes whereas the ten-fingered Vorlakka "...used a decimal system like Earth's." (p. 65) So what is the base number of Kandemirian mathematics?

"That's why I've gone so gutless, [Donnan] thought. Now there's nothing in space or time except my own piddling self.
"The hell there isn't!
"The knowledge burst within him. He sat straight with an oath."
-CHAPTER SEVEN, p. 80.

What knowledge? This is yet another Andersonian moment of realization, initiating yet more reader suspense as we wait to learn what has burst within Donnan.