The Johnsons did not understand they had been conned

[Bassim]

I am wondering if my sentence is grammatically correct.

The Johnsons did not understand they had been conned until they arrived at the seaside and saw that there was no trace of the house they had booked online.

 

[emsr2d2]

I'd probably use "realise" rather than "understood". The latter suggests that they had been made aware of the fact they were being conned but simply failed to understand it.