There is a lump under the wall- to-wall carpet in my master bedroom.
The night before last, I walked into my bedroom, and as I rounded the end of the bed to get to my side, I stepped on a lump. Hmm, a blanket must have slipped off the bed. Turn on the light - no blanket. I walk back over the spot, sure nuf’ there is a definite rise. It was not there that morning, I would have noticed.
Next morning I point it out to my husband. He jumps up & down on it - nothing squeaks or moves, it’s a pretty firm lump. It’s about the size of a big dinner plate and it is about a 18" from the wall and about a foot off to the side of the window, so we look to see if maybe the AC was leaking and caused the sub-floor to swell. Nope - dry carpet. Maybe a section of the subfloor came loose? No, like before, nothing squeaks or moves when we jump on it.
The only way to see what’s going on is to pull up the carpet, but we had a very busy day planned with people coming over for dinner so we’ll said we’ll worry about it later. And today we worked. Well it is later and the lump has gotten taller. It’s about 1 1/2" high.
I’m kind of scared when I open my bedroom door, I keep thinking of Stephen King stories.
How long has the cat been missing?
Are you near Oakland, Michigan? I hear that they had to move Jimmy Hoffa’s body.
No, both cats are accounted for.
We are going to pull up the carpet tomorrow after work. We’re hoping it is not the Golgotha Shit Demon, or the like.
There is hot glue tape that installers use to join edges.
You could use a razor/box cutter and make a clean cut along the weave of the carpet - big enough to look underneath and pull out anything that might be there or make any repairs. Then you put the tape with lines of solid glue on the face under the carpet where the cut edges meet. Then just heat to melt the glue.
I think the pros use a special tool to do the melting, but I’m sure you can improvise and the guys at Lowes or HD can help you out.
edit: the join will be completely invisible unless maybe it’s very, very short pile commercial type carpeting which I’m assuming it’s not.
Op, I’m waiting for a slightly bruised Sherlock Holmes to rise up from your carpet after you leave the room to post something about you in this thread under your sign on. 
Unless you Don’t think Robert Downey Jr would be under your bed…
We put new carpet in my bedroom when I was a teen. One of the knobs from my stereo went missing and yes, there was a lump in the middle of the floor.
I’m sure my brother did it on purpose.
Are you near where that lady released her daughter’s ball python into the neighborhood?
Put some Windex on it.
From the tag of the OP, I was going to suggest getting an appointment with your Gyno. 
Can’t wait until tomorrow.
Do it now, please!
You and my boss think alike! That was his first thought.
That sounded bad, didn’t it, but my boss and I were friends long before I started working for him.
Call an exorcist!
You have cats? Could they have brought something in?
I don’t think cats are carriers of carpet measles.
It might be a tumor.
What about Carpet Mumps?
I think it’s Lupus. It’s really the only thing that makes sense.
It’s not a TOOMAH!
Ha. Beat me to it.