In the episode Lord is my Shepherd, Laura runs away and after the death of her baby brother, Charles Ingalls Jr. She feels guilty when he dies and believes it was because she was jealous of the attention the baby received.
When she ran away, Laura encounters a hermit, Jonathan (played by Ernest Borgnine), when she climbs a mountain to be closer to God. At the end of the episode, Jonathan convinces Laura that God wants her to be with her Pa and the rest of her family.
But was Jonathan really a hermit or was he actually an angel?
The most telling aspect is that only Laura ever saw Jonathan. No one else sees him including her Pa and Mr. Edwards, who were both searching for her. Because Laura could only see him, the implication is that Jonathan is an angel.
As an interesting side note, the next series starring Michael Landon, Highway to Heaven, also featured an angel named Jonathan.