A teenage boy was approached by a man and a woman with a machete in Royston.
The victim was walking along Old North Road at around 9pm on Monday, October 14 when a black Ford Ranger pulled up.
A man and a woman got out of the vehicle and shouted for the boy's attention. It was reported that they were in possession of a machete.
The pair then got back in the vehicle and drove down Orchard Road.
Police are now appealing for anyone with any information or dashcam footage to get in touch.
PC Shane Ludman, who is investigating, said: "I am appealing to anyone who was in the vicinity and may have either seen the incident take place or the vehicle making off afterwards.
"If you have any information, no matter how small, please contact me via shane.ludman@herts.police.uk."
You can also report information online at herts.police.uk/report, speak to an operator in the Force Communications Room via online web chat at herts.police.uk/contact or call the non-emergency number 101, quoting crime reference 41/86170/24.
Alternatively, you can stay anonymous by contacting the independent charity Crimestoppers on 0800 555 111 or via their untraceable online form at crimestoppers-uk.org.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here