Doctor Carrington provides health and medical services to the agents of the intelligence organization known as the Railroad. He is also Desdemona's right-hand man. However, he relates that this has minimal impact. The doctor is easily exasperated and irritated, though he claims this to be because of the Railroad's numerous setbacks and losses. He sometimes questions Desdemona's tendency to send agents on dangerous missions to gather intelligence when said intel is already more or less known.
Having Curie as the Sole Survivor's companion leads to dialogue of her asking Carrington at what university he studied medicine, much to his exasperation. Further dialogue between the two includes inquiries regarding current publications about medicine.
When the Sole Survivor turns over the prototype rescued from the Switchboard during Tradecraft, they might be confronted by Carrington. The Sole Survivor may then ask him "Is there someone you like?". Preston Garvey will dislike this question and interrupt them saying "We're not here to make friends".