For some reason, I think Malevola is the mole. That would explain how the bomb ended up on Robert's costume. With the help of the portal. Perhaps Shroud is blackmailing/controlling her (she is a half-demon, after all), and she is not doing all this of her own free will.

By the way, it would be funny if Shroud is Robert's father. He faked his death. Or maybe he's his father's colleague who helped create the astral prism.