Contains spoilers for this episode and earlier episodes.
The Lightman Group joins security preparations for the wedding of a South Korean ambassador's son. Death threats against the ambassador make political violence the obvious concern, but the groom is shot during the ceremony. A man Lightman identifies as dangerous turns out to be planning to set himself on fire in protest. With the building sealed, the investigators have to find another attacker among guests, relatives and people working at the wedding.
Questioning exposes the groom's gambling and the ambassador's secret connection to his bodyguard, who is another son. Neither secret explains the shooting. Attention shifts towards Phoebe, the bride, whose name and wedding guests conceal her earlier life. When recordings reveal no angry guest watching her, Lightman considers the people behind the cameras. One videographer is Phoebe's former husband, who brought a dismantled weapon through security and targeted the man she had chosen to marry.
The former husband is caught, and Phoebe explains that she wanted to escape an unhappy life. The ambassador and his bodyguard exchange respectful bows after their relationship has been exposed. Torres also works with Secret Service officer Karl Dupree, who asks her out despite her warning that she will notice his lies. Gillian keeps Alec inside the sealed venue when he wants to leave for a supposed work meeting, while Lightman continues to avoid telling her what he suspects.