He was an angel, not the Supernatural kind of angel where they had no control over their minds but a little more like those demons in Death Note except he doesn't like apples and he doesn't kill people. Mycroft was in need of another master, so as to speak but humans were so boring, uninteresting, predictable, hence he was having a hard time trying to find a suitable one.
Sherlock, his brother, had found a human he could tolerate. Good for him, he muses a bit envious because he was hungry and he needed food. Mycroft could steal from the shops but it wasn't in his nature to do so. Carrying his notebook, he wandered the streets in search for any potential human but soon stopped to rest at the bench near the park, away from the crowd.
It was one of his past times to observe humans and what they had been through that day or the family they had, giving him something to do other than…nothing. Backing up against the bench, he folded his legs, book in his lap and stared particularly at one man whose silver hair caught his eye; slouching means something bad had just happened and judging by the clothes he was wearing, officer then. Careless guy though, leaving donut crumbs all over his shirt and a little bit of coffee stain. Single from the lack of a wedding ring, good.
Mycroft was leaning forwards with each observation before he caught himself and instead stood up from the bench, he could help this man and in turn gets what he needs as well. Planning his route, he transported himself a few metres back and runs towards the officer, acting rushed while hitting the other in the shoulder and dropping his book on the floor before hurrying off.