Donovan Boyd. This character, played by Aaron Abrams, makes a good first impression. In the episode, Boyd is new to undercover work, and is the key person in an operation to gain possession of armour piercing [cop killing] bullets.
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We see him talking to the hidden camera, just before a deal is to take place in the room. Boyd is concerned that the sounds of arguing in one of the other apartments might interfere with the recording of the negotiations. He keeps pointing up at an area of the ceiling. In short, Boyd seems totally dedicated, totally professional.
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The first sign of trouble, is that a bit later, he starts to take a real disliking to our heroine, Andy McNally [played by Missy Peregrym].
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Eventually, Boyd will become a most unlikable character. But Donovan Boyd never stops being an important part of the Rookie Blue adventure.