Tani stands in as an instructor at the HPD academy and promises Grover to check on recruit Siobhan, his niece, who after shooting practice confides into Tani that she thinks her near-boyfriend, fellow recruit Endo Tanaka, may 'cheat' on her as he hides a second cellphone. The sister of Joanne, the flame he couldn't save after their car accident, reassures apologetic Danny she doesn't blame him as he did everything he could. Spying alone around Endo's house, Siobhan overhears Endo speaking to his Yakuza liaison, but gets caught and kidnapped to a jungle shack. Five-0 investigate and have HPD intercept Endo, who was told by Kenji Higashi to continue his day as normal. They doubt Endo's story about Siobhan supposedly committed suicide. Morally cornered, Adam risks everything by demanding to exchange Endo for Siobhan with the Yakuza, without coming clean to Steve, who trust him, unlike Grover. A bloody shootout is inevitable.
—KGF Vissers