Who Was On The Other Line?

My house has one story, plus a basement. We have two phones in the house; one in the living room upstairs and one in a room that we use as an office in the basement.

Well, a few nights ago, I was in my living room talking to a friend, and I suddenly heard someone pick up the phone in the basement. Thinking I was imagining things, I ignored it. That is, until my friend asked if someone in my house was listening to our conversation (I was home alone, so that was impossible). As soon as she said that, whoever was downstairs hung up. Fear came over me, obviously, and I told my friend I had to go.

The first thought that entered my head was... had someone found a way into my basement without my knowledge? It never occurred to me that it could have been a ghost. I should have been calling the police or running out of the house... anything but going down to the basement. But, that's what I found myself doing.

When I got to the room, although visibly shaking, I opened the door and peered in. No one there. So, I walked all the way in, looked around, and saw nothing. After I had checked the whole basement and was satisfied with my conclusion that no one was down there, I dismissed the whole incident as just a noise the phone was making (it wasn't exactly new).

Anyway, I decided to go back upstairs to call my friend again and let her know that everything was okay, but when I picked up the receiver, I didn't hear a dial tone, but instead heavy, angry breathing. Fear struck me again. "Who is this?" I asked. No reply. Instead, I heard the person on the other line hang up, and then heard heavy footsteps walking slowly up the stairs. Just when I heard the thing reach the landing, my parents and sister walked through the door, and the footsteps stopped. It still scares me when I think about what could have happened if they hadn't had come home at that very moment.

I guess I should also add that, in that same room with the phone, there's a large closet that was once another room, but the previous owners had put a wall up to block out the other half of the room. Everyone who knows about it thinks there's bodies in there (I have a superstitious family). Maybe we're right, and the ghost of one of the bodies was the one on the phone.