Scientists from the Atomic Weapons Research Institute were conducting experiments with new sources of nuclear energy and discovered these highly radioactive marbles that can trigger a powerful chain reaction when reaching the end of a firing tube. However, further research has shown that the weapon design is not feasible due to the marbles detonating prematurely and potentially causing the entire building to explode.
"Exploit this weakness to destroy the entire chain of radioactive marbles before it reaches the firing point in the tube, or else things will end with a HUGE BOOM tonight."