Without given much preamble, Light looks over the tapes from the TV station and voices the same conclusion as L, that there's a second Kira. With this conclusion validated, they work together to draw out the copycat. It works. The copycat gives a live broadcast reply but it proves a liability to Light when the copycat reveals shinigami information best kept secret. Horrified, L now realizes supernatural forces are involved. Written by
Did You Know?
I learned the only way to kill a shinigami is to make them fall in love with a human.