Masks by Robert J. Crane

What makes a hero?

For years, Sienna Nealon has worked with the U.S. government to protect the world against other people with powers beyond those of a normal human. But after several clashes with the current administration, she finds herself with a new employer, an independent agency dedicated to helping stop threats to humanity. When a new hero and villain rise in New York City, Sienna can’t help but get involved, even as the U.S. government sends its own response team, led by an old friend…and a new enemy.

Soon, Sienna finds herself once more against the odds, against the government, and wondering where the line is between hero and villain.