When your power is nothing you are powerless.

This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. There are a couple possibilities for 力 though, so here's a mnemonic to help you remember which to use:

You know 力 uses its りょく reading here because you're totally powerless when they lock (りょく) you up. Who's "they"? I don't know, but did you hear the click of the lock behind you? That means you're powerless now.