April's first missions for UNCLE were what Mister Waverly termed milk runs. Important, but generally bland and safe. On her seventh assignment, the milk curdled.
Her reactions had been trained into her by Survival School and the continuing training that their CEO, Napoleon Solo, required all field agents to attend. Normally, the dart would not have killed the THRUSH agent. Technically, it didn't kill him. Falling from the roof did that.
April had never caused a death before and stared at the body for several minutes before completing her mission. She didn't throw up until much later.