We all need a partner. Sherlock has his Watson, Robin Hood has his Little John. The Plague Doctor has the Plague Nurse.
Medieval plague doctors thought the smelly herbs and flowers they stuffed in their masks would keep them healthy. They didn't. But their impenetrable (and spooky!) leather outfits actually did!
If you were about to do medieval battle against infectious miasmas armed with only a lantern, a rudimentary concept of personal hygiene, and a beak full of smelly herbs and flowers, you'd want a second-in-command who's got your back.
Now, go wash your hands. Now wash them again.
*Note: there may be some variation in the glow-in-the-dark color of the lantern.