(DM rolls 1d20+4: 20!) You caught the distinct shimmer of illusion when he threw a hood on. You and the spellsword sergeant, Jasper, tail the old woman out of the theater. She glances behind; (DM rolls 1d20: 11!) you're not sure if she saw you. She jogs out of sight down an alleyway. A second later, a startled-looking merchant stumbles out of the alley (DM rolls 1d20: 14!). "Sorcery! Witchcraft!" he shouts, pointing behind him.
I'd like to do an knowledge arcana check and sense motive to see if the merchant is in fact the other person in disguise with some type of magical aid.
Order Jasper to detain the merchant and proceed cautiously into the alley.
Leaving spellswords on guard, you watch the audience. The noble in the private box looks startled to see the curtain rise on living actors. The audience is loudly overjoyed by Leander's clever digs at the Duke. During the last scene, as the audience weeps through Paladinus's dying speech, a servant whispers to the noble. As he leaves his box, (DM rolls 1d20: 17!) he shimmers and becomes a cloaked woman.
Was it a spell or some sort of item-based ability? Bring a spellsword and follow her acting as regular theatre patrons.