Serena surely got Maxwell's 'appreciation' and was practically livid, turning pale at the sight of the finger and the letter but there was nothing she could do but scream and yell at no one in particular.
She blew up in rage, cussing, screaming and yelling like a mad woman. How plans had been ruined. All of it. She couldn't even show her face anywhere because her face was all over every news.
A warning from the German Empire and also the great reveal of all that she had done, including funding and conducting experiments with live humans, trying to perfect the effects of some drug which has the purpose of wiping a person's memory.
The drug made people go mad eventually because they couldn't take the pain in their head. The pounding was so awful that they would rather hit their heads against a wall, causing their heads to bleed but they still wouldn't stop.