Answer:
The detective continued to search for the missing girl.
infinitive: to search
infinitive phrase: to search for the missing girl
Finally, a break in the case appeared to set him in the right direction.
infinitive: to set
infinitive phrase: to set him in the right direction
Just when he started to doubt his plan, he found the scared young girl behind the door to the cabin.
infinitive: to doubt
infinitive phrase: to doubt his plan
Step-by-step explanation: