Caught in the Middle by Regina Jennings and published by Bethany House Publishing.
The train to Garber, Texas, is supposed to bring Nicholas Lovelace to the next victory in his life and career. Instead, it gets held up by robbers who are thwarted by the last person Nick ever expected--Anne Tillerton from back home in Prairie Lea.Anne's been working as a buffalo hunter and hiding from polite society. She's only coming to town to talk their runaway cook into returning. Instead, the woman flees--and leaves Anne with her infant son. With Nick the only person she knows in town who can help, the two form an unlikely team as they try to figure out what to do with the child.