Soon after the discovery of microbial contamination Outside, Alexander was alone in the fish farm pumping room, above Building 29.  It was evening, and everyone else had gone to their homes in lower levels of Building 29 or elsewhere.  Harper was hosting a visit from both Ophelia and Dorothy; the trio had made evening conversations a recurring event.  Not that Alexander was in any way unhappy about this; Harper seemed to be happier after her visits from Ophelia, and she always enjoyed seeing Dorothy, but Alexander himself did not usually find the conversations of these three to relate to topics he had much to say about.  In addition, he had some catch-up work to do on the middle layer of the fish farm, the one with plants growing in the water and a layer of air, sandwiched between the top level (all water, to absorb radiation) and bottom level (where the actual fish were).

Alexander, was not by any means lacking in intelligence.  He was also a careful person, prone to double- and triple-checking his work.  However, he was not by nature a nervous person.  When the pumping station detected excessive vibrations, and the alarm sounded, he did not at first react with anything other than curiousity about the source of the problem.  Had Harper been with him, she would no doubt have been almost immediately upset, and would have insisted that they leave quickly.  However, Harper was not there.  Alexander did not leave.

There is a well-known phenomenon, wherein vibrations from one system, can set up vibrations in another, which then in turn can reinforce the vibrations in the first.  If this is between a speaker and a microphone, we call it "feedback", but it can happen with mechanical vibration as well.  A certain amount of vibration is not unexpected in a pumping system, but if the vibrations of different pumps exacerbate each other, perhaps because the pumps are in close proximity, then it can sometimes result in a bad feedback loop.

Over time, it can also vibrate screws, welds, or other connections loose, and this may result in more vibration (because the pieces of the pump are not all as firmly connected as they should be).  This, combined with any other feedback loops that may exist, can result in a small problem growing rapidly, until something happens that breaks the feedback loop.  For example, by breaking the system that creates it.

It was not possible, afterwards, to determine exactly where in the fish farm the first element broke, but once one did, it caused a cascading catastrophe of broken glass and metal, twisted and shattered under the weight of water that was no longer distributed as it was supposed to be.  Alexander, in the middle layer at the time, was crushed by the weight of water from above, by the drop through the layer below, and pierced by multiple pieces of broken metal and shattered glass.  He did not live long, but he did, just before losing consciousness, have just enough time for a panicked moment of fear.  Not for his own self, but for Harper.  What would she do now, without him there to smile and hold her and tell her it would be ok?

The fish, and plants, lived a bit longer than Alexander.  But not for much longer.