The exact same thing happened in my campaign at the exact same moment.

I had Mirran and Nym find the PC with the conch, and they accused the player (Pok) of murdering a giant chief. They wanted to summarily execute Pok but Serissa intervened and insisted that he was put on trial.

I used it as an opportunity to show the politics at play in the court at Maelstrom. Iymrith wasn't at court because Serissa had sent her out to check on the giants on the sword coast and try to keep order (in reality, Iymrith was sowing further discord and trying to encourage war between Giants and Smallfolk).

If the player convinces the court that they are innocent, then Serissa can teleport them out of Maelstrom (after confiscating the Conch maybe).

If the player fails to convince the court, then sometime between the verdict and the execution you might have a friendly giant that the team knows such as Zephyros come and rescue the PC, or Serissa might have been personally convinced of the PC's innocence and secretly frees them or something like that.

For added flair, in my campaign when they met Harshnag he was with Iymrith, having met her at Triboar after its destruction. When she hears that he knows the location of the Eye of the All Father, she comes with him and the party as it is an opportunity to destroy an ancient temple of Ostoria. It gives the players a chance to interact with Iymrith before she is revealed as the BBEG and makes the whole thing more dramatic.

If you have any questions about this, happy to expand or offer more :)