Your beloved cat is in a completely sealed box impenetrable by any instrument and you cannot see through it or know what is going on inside the box.
There is also a test tube full of poison gas inside the box.
The cat may break the test tube and kill itself.
Opening the box will result in automatic opening of the test tube, and result in the cat's immediate death, but you will then have the knowledge of when the cat actually died, if it broke the test tube before you open the box.
Will you open the box? when? why.