So I was draining the tub in my 1920's era condominium a moment ago when I noticed a substantial amount of water pooling on the floor next to my tub. I soaked it up in a hurry but then I noticed a little more bubbling coming up from under this silver mystery plate next to the tub:
I've used this tub many times before but never had an issue. As soon as the tub had fully drained out the water stopped coming out from under the plate.
What is happening here? I'm totally befuddled. What should i do?