Petra and Michael first meet at the first sonogram in Chapter Two. Almost immediately, after being ushered from the room and left to watch Jane and Rafael experience the scan, they strike up an alliance. Petra wants to stay with Rafael, even if it means raising his and Jane's child – Michael doesn't want the baby.
Once Zaz has been murdered and Petra is suspected complicit, Michael helps her remove crime scene evidence to avoid her arrest and Jane subsequently wanting the baby herself. Later on, Petra threatens that she'll tell of his actions if she is arrested, leading Michael to compromise his own investigation. So, in a nutshell, these two seem to somehow balance each other out and be worthy adversaries, but are incredibly antagonistic toward one another.
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