Take ELF (A).
Talk to the agent (B).
Play the HOP.
You will receive the SILVER BADGE (C).
Give the SILVER BADGE to the agent (F).
Zoom into the unconscious agent; take the POST OFFICE KEY (G).
Zoom into the door; insert the POST OFFICE KEY into the lock (H) and turn the key once.
Enter the Post Office.
Zoom into the letters and use ELF to dig through the letters (I); take the PIN (J).
Zoom into the medicine cabinet and insert the PIN into the lock (K); take the STIMULANT (L).
Zoom into the unconscious agent; inject the STIMULANT into his arm (M).
Talk to the agent (N); you will receive the FIRE EXTINGUISHER.
Extinguish the fire with the FIRE EXTINGUISHER (O).