Didn't my phone have no signal?

How could I receive this call?

"Open the door, I heard your phone ringing."

I gripped my phone tightly, leaning against the door, nervously swallowed my saliva.

Just then, my phone vibrated.

It displayed a message from the delivery rider.

I clicked it open tremblingly.

[Hurry up, my next order is going to be overdue.]

"Forget it, I'll leave it at the doorstep."

As soon as the person outside finished speaking, the lights in my house suddenly went out.

The entire house instantly plunged into darkness.

I looked outside through the peephole, it was pitch black outside, it seemed like there was a power outage.

Did the circuit break?

And at that moment, I actually heard a clear knocking sound.

Not the front door!

It was the bedroom door!

Someone was knocking on my bedroom door!

But, isn't there only me in the house?