The faint laughter was swallowed by the blizzard and did not carry far through the howling wind, so Bruce did not hear it.
At that moment, he was in a guest room on the other side of the manor, changing into his Batman suit.
Earlier, when he had gone to the helicopter to retrieve the engine, it had not entirely been to spite Lex. In fact, Selene could only carry lighter portable equipment, while the complete Batman suit and gear had been left aboard the helicopter. Bruce had brought them back along with the engine.
Just like Lex, after the three of them split up, none of them had actually followed the original plan. Clark had gone to inspect the reception room because of the mysterious phone call, while Lex and Bruce both had their own additional plans.
Lex's first priority was to deal with Lionel's body in the washroom. He had never intended to look for the entrance himself. He planned to wait for Bruce and Clark to finish the work, then reap the benefits.
Bruce had naturally anticipated that. That was why he had no intention of working for Lex either. His plan was to return to the guest room, put on his full Batman gear, and create an entrance by his own methods.
Using a door was a relatively civilized approach, but Batman rarely used that method. Rather than gamble on which of the three of them would find the entrance first, or whether they would share it after finding it, it was better to rely on himself.
Since the entrance was underground, then theoretically, as long as he could blast a passage down below, that would count as an entrance. So Batman's plan was to make a bomb and blow his way down.
There were no