Contrary to what Five believed, Delila was very smart, and once people began to get sick, she knew she caused it. The first time Five came into the house, he helped her, and to help him, Delila dumped the bottle of arsenic crystals into the house floor vents, rinsed the container with water, and filled it with sugar crystals after the container was dry. She needed to keep up the appearance of drugging the water system so 'friend' wouldn't know and keep Lila away from her. But now Five was looking at her like she was the bad guy.
Five said, "I saw you poising the water supply earlier." Delila said, "it was sugar crystals from cousin Lila." Five didn't believe her, and she said, "it was 'friend' who gave me poison, but I'm giving it all back to him, because he is bad, and he keeps poisoning water." Five was about to argue until Delila grabbed an empty bottle with gloves, opened a floor vent, and rubbed the bottle in arsenic, getting the poison inside the water bottle, "I give this bottle to 'friend' for recycling because he's bad, he reuses and drinks bad drug." Then she grabbed the arsenic bottle full of sugar crystals for Five, he smelt them, and it had an odour, so it wasn't arsenic, she was telling the truth.
Hours later, the news broadcasted a worldwide alert for imported water, and vaccines for arsenic poisoning were flown all across the world. Delila sat sadly on the couch under Five's stern eye, "I didn't want to hurt anyone." Five nodded, the authorities came to get Delila, and Five returned back to 2019.
He walked over to Heather, "the commission didn't send me on that mission, did they." She shrugged, Five said, "Lila inadvertently caused an apocalypse and you sabotaged the Commission network to keep it down." Heather's smile answered his accusation.