"The elegant simplicity of Crypto's animal instincts is described, quote, that poor dog just followed his base instincts like we all do in times of unexpected strife. He was just trying to bite a bad man, end quote. This is exactly the drive Kara has lost, and it's poignant then that she too gets injured by the same archer. With Crypto's life on the line, so it seems, Kara takes on Ruth's commission, despite the paradox of being unable to kill. Through their journey together, Crypto is saved, so it seems, and the parallel portion of Kara is likewise restored, ably symbolized with the two standing healthy and strong together in the end. All this is just to say that Crypto's brief but pivotal role in the story is as much symbolic as it is relatable. It sets the plot in motion, it humanizes our broken Supergirl, and it symbolizes the character arc that the series frames. He's a good boy."