Clutch pedal on my car has gone

I used my car last week without incident and was able to park it without any problems in my garage. The temperature last week was about 17 degrees Fahrenheit. When trying to go out in my car today (about 8 days later), with the temperature being 48 degrees, I started the car but when I went to depress the clutch pedal to put it into gear there was no resistance and the pedal just went back, no tension, no pressure, no nothing, and I couldn’t put my car into first gear.

After turning the car off I got out and looked under the car and there was a large damp spot about two feet in diameter which was approximately under the firewall and in the center just about where the transmission bell housing is.

My car has a hydraulic clutch (two cylinders - master and slave) and is not cable operated. The master cylinder is inside the car at the top of the clutch pedal and the slave cylinder is outside and goes into the transmission housing. Since there is a puddle I suspect the slave cylinder has gone.

I am wondering what has happened and whether it is an easy fix. I suspect that, due to the temperature changes and the age of the car, a seal has gone somewhere or a pipe has broken. I have not physically gone under the car to thoroughly check things out.

There is no feeling of the clutch plate being depressed to enable the changing or engaging of gears.