Read the excerpt from a short story. At least ten minutes had passed since the last locker door slammed. I had lurked long enough in the deserte shower stall, ruminating on my devious plan. I emerged to see the vacant room I'd anticipated. Within minutes, I had deciphered the locker combination and opened it without witness. This was my chance to reclaim what was rightfully mine, and I felt my heartbeat escalate.
Which best describes the tone of the excerpt?​