We’re a little late,* but we’re already Toruń.**

* We got stuck on the previous stop of Solec Kujawski for fifteen minutes or so.
** I’m sorry.

Toruń is as far as I will go today. The main station is on the wrong side of the river, though, so would involve a twenty minute walk. Or, if you are lazy and/or booked yourself a room right behind Toruń Miasto station, you could take this suspiciously familiar looking thing for two minutes.
Toruń strikes me as worth spending a bit more time at then arriving after night fall and leaving after breakfast. Very pretty old town with lots and lots of churches.
It is also the birthplace of one Nicolaus Copernicus, inventor of the quantity theory of money (and maybe some other things).
Good morning! Before we continue our journey east, here’s the crossing of the river Wisła which was hidden in the dark last night.
One thing that is cool about eastern Europe is that everyone used the same basic signalling system. So I can tell you that we will be leaving with 40 then line speed without knowing Polish rules.
Quick transfer in Olsztyn where they have a shiny new (if a bit sterile) station building.
The aforementioned Copernicus worked as an administrator here, so they named the new station for him.
My impression of PKP Intercity is that either everything is fine or a complete disaster with little in between.
Kilometre 353 on line 353.
Korsze. It’s a mere twenty kilometres up line 353 to the Russian border and onwards to Chernyakhovsk, which should be called Wystruć or Įsrutis, from where, in a better world I could continue to Klaipėda. Instead we turn southeast towards Ełk and Białystok along a newly renovated line that The Map still shows as not having passenger service. Some corrections are, apparently, required.

That was a fun journey. Until about Ełk the landscape is unexpectedly varied – very hilly with forests and many little and one big lake and things. After that it calms down substantially and becomes more flat and open.

I definitely can recommend going to Białystok this way.

I believe the centre of Białystok is fifteen minutes that way, but the map is inconclusive whether there really is one.

Let’s try something else instead. There is a local service heading northeast departing pretty much right now.

This train has Wifi but no suspension.
Sokółka. The train continues to Kuźnica Białostocka right by the Belorussian border. I would have time to go there and come back for my actual train, but I am not sure how relaxed Polish officials are these days. Better to spend an hour here.
The line continues straight to Vilnius as part of the old Petersburg Warsaw Railway, but as it has to cut through a corner of Belarus to achieve this, we have to do a detour to what is known as the Suwałki Gap, a 65 km stretch of border between Poland and Lithuania a bit to the west, named after the town of Suwałki where incidentally my next train ought to run to.
@partim It's quite ironic how important it is these days, considering it was originally built as a kind of half-circle connecting the towns of Suwalszczyzna/Suvalkija to the Warsaw-Petersburg railway. It ran Grodno/Hrodna-Augustów-Suwałki-Šeštokai-Alytus-Varėna (the present-day Sokółka-Dąbrowa Białostocka section was added after the area was divided by a border, unsurprisingly)
@HaTetsu The borders in this area are really not railway friendly. In Lithuania, Kazlų Rūda – Šeštokai had to be built after 1918 as well.