Terry is tailing passenger 74, Christine Marre.
He's been in her flat, looking for photographs or letters. She's thorough. Obviously trained -- not a letter anywhere. She must read them and eat them. He looked through the wastebin for torn paper. He looked at her phone bills, from Mercury, itemised. No Irish calls. Everything in the flat looks temporary, like she doesn't really live there.
He wants to fuck her. She's the kind of woman he likes; there is something delicious and theatrical about her face. He wants to have an affair with her, and find out all about her husband. And then one night, with his dick up her, he'll tell her: I'm a Provo.
That will make her come; he knows that from her face, from its avidness, its blank stare. She'll be terrified, thrilled. Middle class British bitch.
He decides. Today on the platform, they'll meet. He stirs himself as the train slows, ready to catch up with her.