Lethe thought it suspicious for researchers to secretly come and go around the Alquimia Stronghold, the training and logistics base. Especially when they brought in the Suspicious Box. You got rid of the Alquimia elite researchers and searched their belongings, finding a Lepharist Access Card. It was the same as her access card to the Alquimia Stronghold. Lethe will look for other means to investigate the Suspicious Box.