in tow

Reader's Digest １月号の定番記事 "Smart Animals" からの抜粋です。
記事中のBabettaは猫でSophieは犬です。
One day, while sitting on the verandah, watching their frolicking with amusement, I realised that Babetta was in serious training mode with Sophie. She would run the length of the backyard fence with Sophie in tow, then jump over the fence into the bushland on the other side. Sophie would follow her to the fence but then stop abruptly, unable to clear it.
"tow" に引っ張る意味がありますが、"in tow" は慣用句として覚えた方が良さそうです。
・Oxford English Dictionary: Accompanying or following someone: trying to shop with three children in tow is no joke
・Cambridge English Dictionary: If you go somewhere with a particular person in tow, they are with you: She arrived at the party, with a tall, silver-haired man in tow.