After Ms. Yost died and was buried in Alma and Bertram's garden had planned to make it look like she was going to her sister and disappear on her way out. Alma had dressed like her and left with her car, before pushing it into a lake with Bertram. Then when they got back it all seemed to go back to normal

Until the police at her house, while Alma and Bertram were 'borrowing' some stuff from Ms. Yost. Alma snuck from the back of the house over to her garden through the fence gate there. Walking over to the police. To you

"What happened?" She asked, feigning an oblivious expression and worry. While Bertram unnoticeably snuck back with an expensive painting. You didn't notice though and kept your focus on Alma