One of the agency’s new clients, Weatherman, is receiving mysterious postcards from an unknown person, who Strike and Robin call Postcard. Robin follows up on a hunch and visits the National Portrait Gallery, thinking Postcard could have a connection to the place.

“’The National Portrait Gallery,’ she said. ‘Three of Postcard’s postcards were bought in their gift shop.’” Troubled Blood, Chapter 16

After leaving her meeting with Strike at the Notes Café, Robin walks over to the National Portrait Gallery.

Robin visits the gift shop where she purchases the same three postcards that Weatherman received.

She then walks around the galleries, holding the postcards so that they are visible.

Later, in chapter 26, Robin tells Strike about another postcard Weatherman received.

“’Our weatherman got another postcard yesterday, sent to the television studio. It’s the fourth one bought in the National Portrait Gallery shop, and it’s got an odd message on it.’”

“She pulled the postcard from her bag and handed it over the desk to Strike. The picture on the front reproduced a self-portrait of Joshua Reynolds, his hand shading his eyes in the stereotypical pose of one staring at something indistinct.” Troubled Blood, Chapter 26

You can learn more about the self-portrait of Joshua Reynolds here.

You can find more information about the National Portrait Gallery on their website here or find their location on the map below.