"Ivo!"
Batman's voice reverberated throughout the dark hallway, but received no response. He slowly moved forward, checking for potential traps.
"I'm only here to talk. Show yourself and there won't be any need for confrontation."
No response. Batman heard a door open behind him and rapid footsteps. He instinctively held up his fist behind him, and whoever it was ran headfirst into it. Batman turned around. Some kind of robot was lying on the ground, slightly damaged from the blow. He continued down the hallway. Eventually, he came to a locked door. He could have picked the lock, but he really didn't have the patience to do so at the moment, so he kicked the door down.
"Ivo!"
Still nothing. There was a small lab with multiple electronic devices in the room. In the center, there was a table with a boomerang stuck in it. Batman reached out to grab the boomerang, but when he did, it exploded, throwing him backward. As he got up, he heard a voice from a dark corner of the room.
"G'day, mate."
"Captain Boomerang."
"The one and only."
"What are you doing here?"
"I don't seem to recall that being any of your business."
Boomerang drew another one of his eponymous weapons, but Batman quickly threw smoke pellets.
"Boomerang, he used smoke. I can't see him anymore."
No response.
"Boomerang, what's going on down there?"
Still no response.
"Boomerang!"
"Deadshot."
"What the…"
Deadshot turned around to see Batman.
"What- how did you get…?"
Batman punched him in the face, sending him careening off of the rooftop he was on.
What were these two doing here? And where's Ivo? I need to tell the League.
Batman jumped down to the street and activated his Justice League communicator.
"J'honn? This is Batman. Ivo isn't here. I found Captain Boomerang and Deadshot. There's something fishy going on here – Wait a minute."
He turned off the communicator and backhanded another assailant. He turned around to see that this one was human, and had five allies emerging from an alleyway. Batman sprung into action by knocking two's heads together and twisting the arm of a third to point his gun away. While using number three as a human shield to prevent his two compatriots from opening fire, Batman grabbed the fourth by the head, which he brought down to his raised knee, knocking him out. He then turned his attention back to the third attacker, who he slammed against the wall. He pulled the fifth and final assailant's gun and grabbed him by the scruff of the neck.
"Please don't hurt me! We just do what they tell us!"
"Who's 'they?'"
"Checkmate, they're called. Real shady… I don't know much! We're just hired to get people out of the way!"
"'Out of the way…' What sort of people?"
"Metahumans, mostly. We bring 'em to rendezvous points, some other guys pick 'em up, and we go away. Sometimes we take out anybody who learns too much. That's why we never ask questions! Honest!"
"Thank you for your cooperation."
Batman punched him in the head, knocking him out. He activated his communicator again.
"J'honn, we've got something big down here."
"I'll assemble the League."