The Reversal

The lab mouse Algernon, who received the same procedure, begins to deteriorate and die. Charlie, now a genius, understands exactly what this means for his own future: the gift is temporary, and his own decline has already begun.

The final diary entries mirror the first — spelling errors return, syntax collapses, the childlike voice reemerges. Charlie's last coherent request is heartbreaking in its simplicity: please put flowers on Algernon's grave.